Buy BOOKS at Discounted Price

Visualising The Solid Shapes

Class 8th Mathematics NCERT Exemplar Solution
Exercise
  1. Which amongst the following is not a polyhedron?A. square B. for all C. delta D.…
  2. Which of the following will not form a polyhedron?A. 3 triangles B. 2 triangles…
  3. Which of the following is a regular polyhedron?A. Cuboid B. Triangular prism C.…
  4. Which of the following is a two-Dimensional figure?A. Rectangle B. Rectangular…
  5. Which of the following can be the base of a pyramid?A. Line segment B. Circle C.…
  6. Which of the following 3D shapes does not have a vertex?A. Pyramid B. Prism C.…
  7. Solid having only line segments as its edges is aA. polyhedron B. Cone C. Cylinder…
  8. In a solid if F = V = 5, then the number of edges in this shape isA. 6 B. 4 C. 8…
  9. Which of the following is the top view of the given shape? A. square B. square C.…
  10. The net shown below can be folded into the shape of a cube. The face marked with…
  11. Which of the nets given below will generate a cone? triangle A. g B. theta C.…
  12. Which of the following is not a prism?A. B. u C. delta D. square
  13. We have 4 congruent equilateral triangles. What do we need more to make a…
  14. Side of a square garden is 30 m. If the scale used to draw its picture is 1 cm :…
  15. Which of the following shapes has a vertex.A. theta B. square C. triangle D. 0…
  16. In the given map, the distance between the places is shown using the scale 1 cm :…
  17. Which of the following cannot be true for a polyhedron?A. V = 4, F = 4, E = 6 B.…
  18. In a blueprint of a room, an architect has shown the height of the room as 33 cm.…
  19. The number of hospitals in the town is The following is the map of a town. Based…
  20. The ratio of the number of general stores and that of the ground is The following…
  21. According to the map, the number of schools in the town is The following is the…
  22. Square prism is also called a ………….. . Fill in the blanks to make the statements…
  23. Rectangular prism is also called a …………….. . Fill in the blanks to make the…
  24. In the figure the number of faces meeting at B is …………….. . phi Fill in the…
  25. A pyramid on an n sided polygon has ………… faces. Fill in the blanks to make the…
  26. If a solid shape has 12 faces and 20 vertices, then the number of edges in this…
  27. The given net can be folded to make a ………… . square Fill in the blanks to make…
  28. A solid figure with only 1 vertex is a ………… . Fill in the blanks to make the…
  29. Total number of faces in a pyramid which has eight edges is ……………. . Fill in the…
  30. The net of a rectangular prism has ……………. Rectangles. Fill in the blanks to make…
  31. In a three-dimensional shape, diagonal is a line segment that joins two vertices…
  32. If 4 km on a map is represented by 1 cm, then 16 km is represented by ……….. cm.…
  33. If actual distance between two places A and B is 110 km and it is represented on…
  34. A pentagonal prism has …………… faces. Fill in the blanks to make the statements…
  35. If a pyramid has a hexagonal base, then the number of vertices is …………….. . Fill…
  36. [1 0] is the ……………. View of delta Fill in the blanks to make the statements true:…
  37. The number of cubes in ab are ………… . Fill in the blanks to make the statements…
  38. If the sum of number of vertices and faces in a polyhedron is 14, then the number…
  39. Total number of regular polyhedral is ………… . Fill in the blanks to make the…
  40. A regular polyhedron is a solid made up of ………….. faces. Fill in the blanks to…
  41. For each of the following solids, identify the front, side and top views and…
  42. The other name of cuboid is tetrahedron. State whether the statements are true…
  43. A polyhedron can have 3 faces. State whether the statements are true (T) or false…
  44. A polyhedron with least number of faces is known as a triangular pyramid. State…
  45. Regular octahedron has 8 congruent faces which are isosceles triangles. State…
  46. Pentagonal prism has 5 pentagons. State whether the statements are true (T) or…
  47. Every cylinder has 2 opposite faces as congruent circles, so it is also a prism.…
  48. Euler’s formula is true for all three-dimensional shapes. State whether the…
  49. A polyhedron can have 10 faces, 20 edges and 15 vertices. State whether the…
  50. The top view of State whether the statements are true (T) or false (F).…
  51. The number of edges in a parallelogram is 4. State whether the statements are…
  52. Every solid shape has a unique net. State whether the statements are true (T) or…
  53. Pyramids do not have a diagonal. State whether the statements are true (T) or…
  54. The given shape is a cylinder. square State whether the statements are true (T)…
  55. A cuboid has at least 4 diagonals. State whether the statements are true (T) or…
  56. All cubes are prisms. State whether the statements are true (T) or false (F).…
  57. A cylinder is a 3-D shape having two circular faces of different radii. State…
  58. Based on the given figure, the length of a rectangle in the net of a cylinder is…
  59. If a length of 100 m is represented on a map by 1 cm, then the actual distance…
  60. The model of a ship shown is of height 3.5 cm. The actual height of the ship is…
  61. The actual width of a store room is 280 cm. IF the scale chosen to make its…
  62. Complete the table given below:
  63. How many faces does each of the following solids, have? (a) tetrahedron (b)…
  64. Draw a prism with its base as regular hexagon with one of its face facing you.…
  65. How many vertices does each of the following solids have? (a) Cone (b) Cylinder…
  66. How many edges does each of following solids have? (a) Cone (b) Cylinder (c)…
  67. Look at the shapes given below and state which of these polyhedral using Euler’s…
  68. Count the number of cubes in the given shapes.
  69. Draw the front, side and top view of the given shapes.
  70. Using Euler’s formula, find the value of unknown x, y, z, p, q, r, in the…
  71. Can a polyhedron have V = F = 9 and E = 16? If yes, draw its figure.…
  72. Check whether a polyhedron can have V = 12, E = 6 and F = 8.
  73. A polyhedron has 60 edges and 40 vertices. Find the number of its faces.…
  74. Find the number of faces in the given shapes:
  75. A polyhedron has 20 faces and 12 vertices. Find the edges of the polyhedron.…
  76. A solid has forty faces and, sixty edges. Find the number of vertices of the…
  77. Draw the net of a regular hexahedron with side 3 cm. (Hint : Regular hexahedron -…
  78. Draw the net of a regular tetrahedron with side 6 cm.
  79. Draw the net of the following cuboid:
  80. Match the following
  81. Complete the table given below by putting tick mark across the respective…
  82. Draw the net of the following shape. square
  83. Draw the net of the following solid: left arrow
  84. Find the number of cubes in the base layer of the following figure. 8 %…
  85. In the above figure, if only shaded cubes are visible from the top, draw the base…
  86. How many faces, edges and vertices does a pyramid have with n sided polygon as…
  87. Draw a figure that represents your mathematics textbook. What is the name of this…
  88. In the given figures, identify the different shapes involved. 9
  89. What figure is formed if only the height of a cube increased or decreased?…
  90. Use isometric dot paper to draw each figure? (a) A tetrahedron (b) A rectangular…
  91. Identify the nets given below and mention the name of the corresponding solid in…
  92. Draw a map of your school playground. Mark all necessary places like 2 library,…
  93. Refer to the given map to answer the following questions. (a) What is the…
  94. Look at the map given below. Answer the following questions. (a) Which two…
  95. Look at the map given below : Now answer the following questions. (a) Name the…
  96. A photographer uses a computer program to enlarge a photograph. What is the scale…
  97. The side of a square board is 50 cm. A student has to draw its image in her…
  98. The distance between school and house of a girl is given by 5 cm in a picture,…
  99. Use a ruler to measure the distance in cm between the places joined by dotted…
  100. The actual length of a painting was 2 m. What is its length in the photograph if…
  101. Find the scale. (a) Actual size 12 m Drawing size 3 cm (b) Actual size 45 feet…
  102. In a town, an ice cream parlour has displayed an ice cream sculpture of height…

Exercise
Question 1.

Which amongst the following is not a polyhedron?
A.

B.

C.

D.


Answer:

Option (a) is a polyhedron because it satisfies its definition which is the solid is made up of polygonal region called faces and these faces meet at edges called line segments and the edges meet at vertices are called point.


(b) is a polyhedron because it satisfies its definition which is the solid is made up of polygonal region called faces and these faces meet at edges called line segments and the edges meet at vertices are called point.


(c) is not a polyhedron because it does not satisfy its definition. The figure contains circular base.


(d) is a polyhedron because it satisfies its definition which is the solid is made up of polygonal region called faces and these faces meet at edges called line segments and the edges meet at vertices are called point.


Question 2.

Which of the following will not form a polyhedron?
A. 3 triangles

B. 2 triangles and 3 parallelograms

C. 8 triangles

D. 1 pentagon and 5 triangles


Answer:

Option (a) will not form a polyhedron because it must have more than four faces. So, it is not possible in 3 triangles which have 3 faces only.


(b) 2 triangles and 3 parallelograms form a polyhedron which satisfies its definition. The solid is made up of polygonal region called faces and these faces meet at edges called line segments and the edges meet at vertices are called point.


(c) 8 triangles can form a polyhedron because it has 8 faces.


(d) 1 pentagon and 5 triangles form a polyhedron which satisfies its definition. The solid is made up of polygonal region called faces and these faces meet at edges called line segments and the edges meet at vertices are called point.


Question 3.

Which of the following is a regular polyhedron?
A. Cuboid

B. Triangular prism

C. Cube

D. Square prism


Answer:

Option (a) cuboid is not a regular polyhedron because its vertices are not formed by the same number of faces.


(b) Triangular prism is not a regular polyhedron which has two triangular face and three rectangular sides. so, vertices are not formed by the same number of faces.


(c) cube is a regular polyhedron because its vertices are formed by the same number of faces.


(d) Square prism is not a regular polyhedron because its vertices are not formed by the same number of faces.


Question 4.

Which of the following is a two-Dimensional figure?
A. Rectangle

B. Rectangular Prism

C. Square Pyramid

D. Square Prism


Answer:

Option (a) is a two-dimensional figure because it has two dimensions length and breadth


(b) Rectangular prism is a three-dimensional figure it has length, width and height


(c) Square Pyramid is a three-dimensional figure, its faces have 4 triangles and one square


(d) Square prism is a three-dimensional figure, it has two square bases and flat sides


Question 5.

Which of the following can be the base of a pyramid?
A. Line segment

B. Circle

C. Octagon

D. Oval


Answer:

Option (a) cannot be the base of a pyramid because pyramid is a polyhedron and its base is polygon.


(b) Circle cannot be the base of a pyramid because pyramid is a polyhedron and its base is polygon.


(c) Octagon can be the base of a pyramid because it has a polygon as a base and lateral faces are triangle.


(d) Oval cannot be the base of a pyramid because pyramid is a polyhedron and its base is polygon


Question 6.

Which of the following 3D shapes does not have a vertex?
A. Pyramid

B. Prism

C. Cone

D. Sphere


Answer:

Option (a) The point at which two or more edges meets is called vertex. Pyramid has atleast 4 vertices.


(b) The point at which two or more edges meets is called vertex. Prism has atleast 6 vertices.


(c) The point at which two or more edges meets is called vertex. Cone has one vertex.


(d) The point at which two or more edges meets is called vertex. Sphere does not have any vertex and edge.


Question 7.

Solid having only line segments as its edges is a
A. polyhedron

B. Cone

C. Cylinder

D. Polygon


Answer:

Option (a) a polyhedron is the solid is made up of polygonal region called faces and these faces meet at edges called line segments and the edges meet at vertices are called point. So it has only line segments as its edge.


(b)Cone does not have only line segment. It is connecting with line and a half line also.


(c) Cylinder having two plane surfaces meeting at the point.


(d) Polygon also contain plane surface not only the line segment.


Question 8.

In a solid if F = V = 5, then the number of edges in this shape is
A. 6

B. 4

C. 8

D. 2


Answer:

According to Euler’s formula, F + V-E = 2 where F = face, V = vertices and E = edge


So, from the given F = V = 5


⇒ 5 + 5-E = 2


⇒ 10-E = 2


⇒ E = 10-2


⇒ E = 8


Option (a) is not match to our solution. so it is not a correct answer.


(b) is not match to our solution. so it is not a correct answer.


(c) is the correct answer and matches with our solution.


(d) is not match to our solution. so it is not a correct answer.


Question 9.

Which of the following is the top view of the given shape?


A.

B.

C.

D.


Answer:

The top view of the shape is determined by the view from the top of a given picture. Here the given shape is



The view from the top of this shape is



Option (a) is the correct answer


(b) is not match to our solution


(c) is not match to our solution


(d) is not match to our solution


Question 10.

The net shown below can be folded into the shape of a cube. The face marked with the letter L is opposite to the face marked with which letter?


A. M

B. N

C. Q

D. O


Answer:

The shape of a cube is follows



If the given picture is folded into cube, N will opposite to P,Q is on the top and O in the bottom. so, L faces opposite to M.


Option (a) is the correct answer matches the solution.


(b) is not match to our solution


(c) is not match to our solution


(d) is not match to our solution


Question 11.

Which of the nets given below will generate a cone?


A.

B.

C.

D.


Answer:

Option (a) cone is a three-dimensional shape which have circular base and it tapers from a base to a point called vertex. This figure have circular base so it is the correct answer.


(b) this figure does not have any circular base so it is not the correct answer.


(c) this figure does not have any circular base so it is not the correct answer.


(d) this figure does not have any circular base so it is not the correct answer.


Question 12.

Which of the following is not a prism?
A.

B.

C.

D.


Answer:

Option (a) is a prism because the sides are congruent.


(b) is not a prism because top and bottom faces are not congruent in the picture. so it is the correct answer.


(c) is a prism because the sides are congruent.


(d) is a prism because the sides are congruent.


Question 13.

We have 4 congruent equilateral triangles. What do we need more to make a pyramid?
A. An equilateral triangle

B. A square with same side length as of triangle.

C. 2 equilateral triangles with side length same as triangle.

D. 2 squares with side length same as triangle.


Answer:

A pyramid is a polyhedron whose base is a polygon and its lateral faces are triangles. we have 4 congruent equilateral triangle, as per definition of pyramid if we add a square with same side length of a triangle we get a polygon as its base and it will make pyramid.


Option (a) is not enough to make pyramid as per solution.


(b) is the correct answer and it is enough to make pyramid.


(c) is not enough to make pyramid as per solution.


(d) is not enough to make pyramid as per solution.


Question 14.

Side of a square garden is 30 m. If the scale used to draw its picture is 1 cm : 5 m, the perimeter of the square in the picture is
A. 20 cm

B. 24 cm

C. 28 cm

D. 30 cm


Answer:

Given, the side of a square = 30m


The formula for perimeter of the square = 4 × side


∴ the perimeter of the square = 4 × 30 = 120m


The scale used to draw its picture is 1 cm : 5 m


Hence the perimeter of a square =


= 24 cm


Option (a) is not match to our solution. so it is not a correct answer.


(b) is the correct answer and matches with our solution.


(c) is not match to our solution. so it is not a correct answer.


(d) is not match to our solution. so it is not a correct answer.


Question 15.

Which of the following shapes has a vertex.
A.

B.

C.

D.


Answer:

Option (a) is not correct because vertex is a point where two or more edges meet. this picture does not have edges.


(b) is not correct because vertex is a point where two or more edges meet. this picture does not have edges.


(c) is a correct answer because vertex is a point where two or more edges meet. this picture have edge.


(d) is not correct because vertex is a point where two or more edges meet. this picture does not have edges.


Question 16.

In the given map, the distance between the places is shown using the scale 1 cm : 0.5 km. Then the actual distance (in km) between school and the book shop is


A. 1.25

B. 2.5

C. 2

D. 1.1


Answer:

In the given map, the scale 1 cm: 0.5 km


The distance between the between school and the book shop in the map is 2.2cm


So, the actual distance between school and the book shop = 2.2 × 0.5 km


= 1.1 km


Option (a) is not match to our solution. so it is not a correct answer.


(b) is not match to our solution. so it is not a correct answer.


(c) is not match to our solution. so it is not a correct answer.


(d) is the correct answer and matches with our solution.


Question 17.

Which of the following cannot be true for a polyhedron?
A. V = 4, F = 4, E = 6

B. V = 6, F = 8, E = 12

C. V = 20, F = 12, E = 30

D. V = 4, F = 6, E = 6


Answer:

Option (a) V = 4, F = 4, E = 6


According to Euler’s formula, F + V-E = 2 where F = face, V = vertices and E = edge


So, from the given


⇒ 4 + 4-6 = 2


⇒ 8-6 = 2


⇒ 2 = 2


⇒LHS = RHS. it is true for a polyhedron


(b) V = 6, F = 8, E = 12


According to Euler’s formula, F + V-E = 2 where F = face, V = vertices and E = edge


So, from the given


⇒ 8 + 6-12 = 2


⇒ 14-12 = 2


⇒ 2 = 2


⇒LHS = RHS. it is true for a polyhedron


(c) V = 20, F = 12, E = 30


According to Euler’s formula, F + V-E = 2 where F = face, V = vertices and E = edge


So, from the given


⇒ 12 + 20-30 = 2


⇒ 32-30 = 2


⇒ 2 = 2


⇒LHS = RHS. it is true for a polyhedron


(d) V = 4, F = 6, E = 6


According to Euler’s formula, F + V-E = 2 where F = face, V = vertices and E = edge


So, from the given


⇒ 6 + 4-6 = 2


⇒ 10-6 = 4 = LHS


⇒ RHS = 2


⇒ LHS ≠ RHS. it is not true for a polyhedron


Question 18.

In a blueprint of a room, an architect has shown the height of the room as 33 cm. If the actual height of the room is 330 cm, then the scale used by her is
A. 1:11

B. 1:10

C. 1:100

D. 1:3


Answer:

From the given, height of the room in blueprint = 33 cm


The actual height of the room = 330 cm


Then,




So, the scale is 1:10


Option (a) is not match to our solution. so it is not a correct answer.


(b) is the correct answer and matches our solution.


(c) is not match to our solution. so it is not a correct answer.


(d) is not match to our solution. so it is not a correct answer.


Question 19.

The following is the map of a town. Based on it answer question.



The number of hospitals in the town is
A. 1

B. 2

C. 3

D. 4


Answer:

From the map, denotes the hospital.so count the in the map, we get 2


Option (a) is not match to our solution. so it is not a correct answer.


(b) is the correct answer and matches our solution.


(c) is not match to our solution. so it is not a correct answer.


(d) is not match to our solution. so it is not a correct answer.


Question 20.

The following is the map of a town. Based on it answer question.



The ratio of the number of general stores and that of the ground is
A. 1:2

B. 2:1

C. 2:3

D. 3:2


Answer:

From the map, we can count the number of general stores is 6 and the number of the ground is 4.





Option (a) is not match to our solution. so it is not a correct answer.


(b) is not match to our solution. so it is not a correct answer.


(c) is not match to our solution. so it is not a correct answer.


(d) is the correct answer and matches our solution.


Question 21.

The following is the map of a town. Based on it answer question.



According to the map, the number of schools in the town is
A. 4

B. 3

C. 5

D. 2


Answer:

From the map, denotes the school.so count the in map, we get 5


Option (a) is not match to our solution. so it is not a correct answer.


(b) is not match to our solution. so it is not a correct answer.


(c) is the correct answer and matches with our solution.


(d) is not match to our solution. so it is not a correct answer.


Question 22.

Fill in the blanks to make the statements true:

Square prism is also called a ………….. .


Answer:


A square prism is a three-dimensional solid object who’s base and sides are all squares. Since all the angles are right angles and all the sides are equal, it can also be called a cube.


Question 23.

Fill in the blanks to make the statements true:

Rectangular prism is also called a …………….. .


Answer:


A rectangular prism is a three-dimensional solid object who’s base is a square but sides are all rectangles. Since all the angles are right angles and the opposite sides are equal, it can also be called a cuboid.


Question 24.

Fill in the blanks to make the statements true:

In the figure the number of faces meeting at B is …………….. .



Answer:

Let us rename the edges in the figure. Now we see that there are 6 faces in total, namely ABC, ABD, EBC, EBD, CDE and CDA. The faces meeting at B have the letter B in it. From the figure, it is evident that the faces meeting at B are ABC, ABD, BCE&BED.(4)


Question 25.

Fill in the blanks to make the statements true:

A pyramid on an n sided polygon has ………… faces.


Answer:

Each side in a polygon contributes to 1 face and an the n sided polygon itself, so if there are n sides in a polygon there will be n+1 faces.


Question 26.

Fill in the blanks to make the statements true:

If a solid shape has 12 faces and 20 vertices, then the number of edges in this solid is ……… .


Answer:

According to Euler’s formula, in any solid (Faces)+(Vertices)=(Edges)+2 or F+V=E+2

Therefore, 12+20=x+2 gives x=20


Question 27.

Fill in the blanks to make the statements true:

The given net can be folded to make a ………… .



Answer:

When the net is folded, it gives


Which is a triangular prism.


Question 28.

Fill in the blanks to make the statements true:

A solid figure with only 1 vertex is a ………… .


Answer:

By definition, A cone is a three-dimensional geometric shape that tapers smoothly from a flat base to a point called the apex or vertex.


Question 29.

Fill in the blanks to make the statements true:

Total number of faces in a pyramid which has eight edges is ……………. .


Answer:

From formula, F+V=E+2, since E=8, F+V must be 10. We know that in any pyramid, the number of faces = the number of vertices. Therefore, 2F=10 gives F=5.


Question 30.

Fill in the blanks to make the statements true:

The net of a rectangular prism has ……………. Rectangles.


Answer:


From the figure, it is evident that the rectangular prism when unfolded contains 6 rectangles.


[Hint : Every square is a rectangle but every rectangle is not a square.]


Question 31.

Fill in the blanks to make the statements true:

In a three-dimensional shape, diagonal is a line segment that joins two vertices that do not lie on the …………… face.


Answer:

If a line segment joins two vertices that lie on the same face, then it is called an edge. However, if a line segment joins two vertices that do not lie on the same face, it is a diagonal.


Question 32.

Fill in the blanks to make the statements true:

If 4 km on a map is represented by 1 cm, then 16 km is represented by ……….. cm.


Answer:

4km→1 cm

16km→x cm


By the method of cross multiplication, we have x = 16/4 = 4 cm.


Question 33.

Fill in the blanks to make the statements true:

If actual distance between two places A and B is 110 km and it is represented on a map by 25 mm. Then the scale used is ………….. .


Answer:

In such problems, it is necessary to convert the given quantities into the same unit. For simplicity, let us convert the actual distance given in kilometres to millimetres.

110km = 110000000mm


Therefore Scale = 110000000mm/25mm = 4400000


So, the scale will be 4400000:1


Question 34.

Fill in the blanks to make the statements true:

A pentagonal prism has …………… faces.


Answer:

Each side in a prism contributes to 1 face and counting the top and the bottom faces of the prism so if there are 5 sides in a pentagon there will be 5+2=7 faces.


Question 35.

Fill in the blanks to make the statements true:

If a pyramid has a hexagonal base, then the number of vertices is …………….. .


Answer:

Hexagonal base contains 6 vertices. Since the problem talks about a pyramid, it is constructed on to another vertex. Total, we have 7 vertices.


Question 36.

Fill in the blanks to make the statements true:

is the ……………. View of


Answer:

given figure is the top view of hut.


Question 37.

Fill in the blanks to make the statements true:

The number of cubes in are ………… .


Answer:

The front row contains 4 cubes and so does the row in the back. In total, we count 4+4=8 cubes.


Question 38.

Fill in the blanks to make the statements true:

If the sum of number of vertices and faces in a polyhedron is 14, then the number of edges in that shape is ………………. .


Answer:

From Euler’s formula, we have F+V=E+2 and from the problem, F+V=14 gives E+2=14, or E=12.


Question 39.

Fill in the blanks to make the statements true:

Total number of regular polyhedral is ………… .


Answer:

Tetrahedron, Cube, Octahedron, Dodecahedron and Icosahedron.


Question 40.

Fill in the blanks to make the statements true:

A regular polyhedron is a solid made up of ………….. faces.


Answer:

4, 6, 8, 12 or 20


Question 41.

Fill in the blanks to make the statements true:

For each of the following solids, identify the front, side and top views and write it in the space provided.

(a)

(b)

(c)

(d)


Answer:

(i) Front View


(ii) Side View


(iii) Top View


(b) (i) Side View


(ii) Top View


(iii) Front View


(c) (i) Front View


(ii) Top View


(iii) Side View


(d) (i) Side View


(ii) Front View


(iii) Top View


Question 42.

State whether the statements are true (T) or false (F).

The other name of cuboid is tetrahedron.


Answer:

The other name for cuboid is square prism.


Question 43.

State whether the statements are true (T) or false (F).

A polyhedron can have 3 faces.


Answer:

The minimum faces a polyhedron can have is 4.


Question 44.

State whether the statements are true (T) or false (F).

A polyhedron with least number of faces is known as a triangular pyramid.


Answer:

The minimum faces a polyhedron can have is 4 and is called a triangular pyramid or a tetrahedron.


Question 45.

State whether the statements are true (T) or false (F).

Regular octahedron has 8 congruent faces which are isosceles triangles.


Answer:

A regular octahedron has 8 congruent faces which are equilateral triangles.


Question 46.

State whether the statements are true (T) or false (F).

Pentagonal prism has 5 pentagons.


Answer:

A pentagonal prism has 7 faces which include two pentagonal faces.


Question 47.

State whether the statements are true (T) or false (F).

Every cylinder has 2 opposite faces as congruent circles, so it is also a prism.


Answer:

Even though the cylinder has two opposite faces, the requirement of a prism is the solid to have flat faces. The cylinder does not have all faces flat.


Question 48.

State whether the statements are true (T) or false (F).

Euler’s formula is true for all three-dimensional shapes.


Answer:

Euler’s formula is only true for a polyhedron that doesn’t intersect itself.


Question 49.

State whether the statements are true (T) or false (F).

A polyhedron can have 10 faces, 20 edges and 15 vertices.


Answer:

F+V=E+2 formula tells us that 10+15 is not equal to 20+2, so it is not possible for a polyhedron to have 10 faces, 20 edges and 15 vertices.


Question 50.

State whether the statements are true (T) or false (F).

The top view of



Answer:

T


Question 51.

State whether the statements are true (T) or false (F).

The number of edges in a parallelogram is 4.


Answer:


Question 52.

State whether the statements are true (T) or false (F).

Every solid shape has a unique net.


Answer:

A net is a figure obtained when a three-dimensional object is opened. Since a 3D object can be opened from any edge, the solid shape has more than one unique net.


Question 53.

State whether the statements are true (T) or false (F).

Pyramids do not have a diagonal.


Answer:

In a pyramid, it is not possible to have two opposite vertices. So there cannot be a diagonal, which by definition is the line segment joining two opposite vertices.


Question 54.

State whether the statements are true (T) or false (F).

The given shape is a cylinder.



Answer:

A cylinder has two circular faces of equal radius.


Question 55.

State whether the statements are true (T) or false (F).

A cuboid has at least 4 diagonals.


Answer:

In a cuboid, the number of diagonals is 4.


Question 56.

State whether the statements are true (T) or false (F).

All cubes are prisms.


Answer:

A cube has opposite faces which are equal.


Question 57.

State whether the statements are true (T) or false (F).

A cylinder is a 3-D shape having two circular faces of different radii.


Answer:

A cylinder is a 3D shape having two circular opposite faces of same radii.


Question 58.

State whether the statements are true (T) or false (F).

Based on the given figure, the length of a rectangle in the net of a cylinder is same as circumference of circles in its net.



Answer:

(T)


Question 59.

State whether the statements are true (T) or false (F).

If a length of 100 m is represented on a map by 1 cm, then the actual distance corresponmding to 2 cm is 200 m.


Answer:

The scale is 10000:1


Question 60.

State whether the statements are true (T) or false (F).

The model of a ship shown is of height 3.5 cm. The actual height of the ship is 210 cm if the scale chosen is 1:60.



Answer:

If the scale is 1:60, then the height 3.5cm will become 3.5x60 cm = 210cm


Question 61.

State whether the statements are true (T) or false (F).

The actual width of a store room is 280 cm. IF the scale chosen to make its drawing is 1:7, then the width of the room in the drawing will be 40 cm.


Answer:

The scale given is 1:7, so the width of the room in the drawing will be 280cm/7= 40cm.


Question 62.

Complete the table given below:



Answer:



Question 63.

How many faces does each of the following solids, have?

(a) tetrahedron (b) Hexahedron

(c) Octagonal Pyramid (d) Octahedron


Answer:

(a)tetrahedron:-4

(b) Hexahedron:-6


(c) Octagonal Pyramid:-9


(d) Octahedron:-8



Question 64.

Draw a prism with its base as regular hexagon with one of its face facing you. Now draw the top view, front view and side view of this solid.


Answer:

The is drawing with top, side, front view given below



Question 65.

How many vertices does each of the following solids have?

(a) Cone (b) Cylinder

(c) Sphere (d) Octagonal Pyramid

(e) Tetrahedron (f) Hexagonal Prism


Answer:

(a) Cone:-1

(b) Cylinder:-0


(c) Sphere:-0


(d) Octagonal Pyramid:-1


(e) Tetrahedron:-4


(f) Hexagonal Prism:-12



Question 66.

How many edges does each of following solids have?

(a) Cone (b) Cylinder

(c) Sphere (d) Octagonal Pyramid

(e) Hexagonal Prism (f) Kaleidoscope


Answer:

(a) Cone:-1

(b) Cylinder:-2


(c) Sphere :-0


(d) Octagonal Pyramid:-16


(e) Hexagonal Prism:-18


(f) Kaleidoscope:-9



Question 67.

Look at the shapes given below and state which of these polyhedral using Euler’s formula are.



Answer:

(a) Edge-9, vetrices:-6, face:-5

By using Euler’s formula


F + V = E + 2


⟹ 5 + 6 = 9 + 2


⟹ 11 = 11. Therefore it is a polyhedral.


(b) Edge-12, vetrices:-8, face:-6


By using Euler’s formula


⟹ F + V = E + 2


⟹ 6 + 8 = 12 + 2


⟹ 14 = 14.therfore it is a polyhedral.


(c) Edge-2, vertices:-0, face:-3


By using Euler’s formula


F + V = E + 2


⟹ 3 + 0 = 2 + 2


.Hence it is not possible. Therefore it is not a polyhedral.


(d) Edge-15, vetrices:-10, face:-7


By using Euler’s formula


F + V = E + 2


⟹ 7 + 10 = 15 + 2


⟹ 17 = 17


Therefore, it is a polyhedral.


(e) Edge-9, vertices:-6,face:-5


By using Euler’s formula


F + V = E + 2


⟹ 5 + 6 = 9 + 2


⟹ 11 = 11 therefore it is a polyhedral.


(f) Edge-2, vertices:-0, face:-3


By using Euler’s formula


F + V = E + 2


⟹ 3 + 0 = 2 + 2⟹


It is not possible. Therefore, it is not polyhedral.


(g) Edge-20, vertices:-11, face:-11


By using Euler’s formula


F + V = E + 2


⟹ 11 + 11 = 20 + 2


⟹ 22 = 22. Therefore, it is a polyhedral.


(h) Edge-16, vertices:-9,face:-9


By using Euler’s formula


F + V = E + 2


⟹ 9 + 9 = 16 + 2


⟹ 18 = 18. Therefore it is a polyhedral.


(i) Edge-18, vertices:-12, face:-8


By using Euler’s formula


F + V = E + 2


⟹ 8 + 12 = 18 + 2


⟹ 20 = 20. Therefore it is a polyhedral.


(j) Edge-12, vertices:-6,face:-8


By using Euler’s formula


F + V = E + 2


⟹ 8 + 6 = 12 + 2


⟹ 14 = 14. Therefore it is a polyhedral.


(k) Edge-0, vetrices:-1, face:-2


By using Euler’s formula


F + V = E + 2


⟹ 2 + 1 = 0 + 2


⟹ 32. It is not possible. Therefore it is not a polyhedral.


(l) Edge-24, vetrices:-16, face:-10


By using Euler’s formula


F + V = E + 2


⟹ 10 + 16 = 24 + 2


⟹ 26 = 26. Therefore it is a polyhedral.


(m) Edge-1, vetrices:-0, face:-1


By using Euler’s formula


F + V = E + 2


⟹ 1 + 0 = 1 + 2


⟹ 13.it is not possible. Therefore it is not a polyhedral.



Question 68.

Count the number of cubes in the given shapes.



Answer:

(a) number of cube are 10

(b) number of cube are 10


(c) number of cube are 10


(d) number of cube are 9


(e) number of cube are 11


(f) number of cube are 9


(g) number of cube are 11


(h) number of cube are 110


(i) number of cube are 113


(j) number of cube are 66


(k) number of cube are 15


(l) number of cube are 14



Question 69.

Draw the front, side and top view of the given shapes.



Answer:

(a) The front, side and top view of the given shapes are given below


(b) the front, side and top view of the given shapes are given below



(c) the front, side and top view of the given shapes are given below



(d) the front, side and top view of the given shapes are given below



(e) the front, side and top view of the given shapes are given below



(f) The front, side and top view of the given shapes are given below



(g) The front, side and top view of the given shapes are given below



(h) The front, side and top view of the given shapes are given below



(i) The front, side and top view of the given shapes are given below



(j) The front, side and top view of the given shapes are given below




Question 70.

Using Euler’s formula, find the value of unknown x, y, z, p, q, r, in the following table.



Answer:

Given that (i) face = 7, vertices = 10, edge = x

By using Euler’s formula


We know that


Face + vertices = edge + 2


⟹ 7 + 10 = x + 2


⟹ 17 = x + 2


⟹ X = 17-2


⟹ X = 15.


Given that (ii) face = y, vertices = 12, edge = 18


By using Euler’s formula


We know that


Face + vertices = edge + 2


⟹ y + 12 = 18 + 2


⟹ y + 12 = 20


⟹ y = 20-12


⟹ y = 8


Given that (iii) face = 9, vertices = z, edge = 16


By using Euler’s formula


We know that


Face + vertices = edge + 2


⟹ 9 + z = 16 + 2


⟹ 9 + z = 18


⟹ Z = 18-9


⟹ Z = 9.


Given that (iv) face = p, vertices = 6, edge = 12


By using Euler’s formula


We know that


Face + vertices = edge + 2


⟹ P + 6 = 12 + 2


⟹ P + 6 = 14


⟹ P = 14-6


⟹ P = 12.


Given that (v) face = 6, vertices = q, edge = 12


By using Euler’s formula


We know that


Face + vertices = edge + 2


⟹ 6 + q = 12 + 2


⟹ 6 + q = 14


⟹ q = 14-6


⟹ q = 8


Given that (vi) face = 8, vertices = 11,edge = r


By using Euler’s formula


We know that


Face + vertices = edge + 2


⟹ 8 + 11 = r + 2


⟹ 19 = r + 2


⟹ r = 19-2


⟹r = 17



Question 71.

Can a polyhedron have V = F = 9 and E = 16? If yes, draw its figure.


Answer:

according to the data given in question

Vertices (V) = Face (F) = 9 and Edge (E) = 16


By Euler’s formula we know that


Face + Vertices = Edge + 2


Face + vertices = 9 + 9 = 18


Edge + 2 = 16 + 2 = 18


Therefore Face + Vertices = Edge + 2 = 18



So, the polyhedron is possible for the above data.



Question 72.

Check whether a polyhedron can have V = 12, E = 6 and F = 8.


Answer:

according to the data given in question

Vertices (V) = 12, Face(F) = 8 and Edge(E) = 6


By Euler’s formula we know that


Face + Vertices = Edge + 2


So,Face + vertices = 8 + 12 = 20


and Edge + 2 = 6 + 2 = 8


⟹ 208


Therefore Face + VerticesEdge + 2


So, the polyhedron is not possible for the above data



Question 73.

A polyhedron has 60 edges and 40 vertices. Find the number of its faces.


Answer:

according to the data given in question

Vertices = 40, Face = ? and Edge = 6


By Euler’s formula we know that


Face + Vertices = Edge + 2


⟹ Face + 40 = 60 + 2


⟹ Face + 40 = 62


⟹ Face = 62-40


⟹ Face = 22.



Question 74.

Find the number of faces in the given shapes:



Answer:

for figure given below:-


number of faces are 14



for the above figure, the number of faces are 10



for the above figure, the no of faces are 16



Question 75.

A polyhedron has 20 faces and 12 vertices. Find the edges of the polyhedron.


Answer:

according to the data given in question

Vertices = 12, Face = 20 and Edge = ?


By Euler’s formula we know that


Face + Vertices = Edge + 2


⟹ 12 + 20 = edge + 2


⟹ 32 = edge + 2


⟹ Edge = 32-2


⟹ Edge = 30.



Question 76.

A solid has forty faces and, sixty edges. Find the number of vertices of the solid.


Answer:

according to the data given in question

Vertices = ?, Faces = 40 and Edge = 60


By Euler’s formula we know that


Face + Vertices = Edge + 2


⟹ 40 + vertice = 60 + 2


⟹ 40 + vertice = 62


⟹ Vertices = 62-40


⟹ Vertices = 22.



Question 77.

Draw the net of a regular hexahedron with side 3 cm. (Hint : Regular hexahedron – cube)


Answer:

Given below is the net drawing of regular hexahedron with side as 3cm each.



Question 78.

Draw the net of a regular tetrahedron with side 6 cm.


Answer:

given below is the net drawing of regular tetrahedron with side 6cm.



Question 79.

Draw the net of the following cuboid:



Answer:

The net drawing is given below



Question 80.

Match the following



Answer:

(a) :-(b)hexagonal.


It has a hexagon at it both the side.


(b):- :-(d)cone


It has a cone like shape.


(c) :-(c) square pyramid


It has square shape base with triangular faces.


(d) :-(a) hexahedron


It is a cone and cone is also called hexahedron.



Question 81.

Complete the table given below by putting tick mark across the respective property found in the solids mentioned.



Answer:



Question 82.

Draw the net of the following shape.



Answer:

The net drawing is



Question 83.

Draw the net of the following solid:



Answer:

the net solid drawing of the above question is



Question 84.

Find the number of cubes in the base layer of the following figure.



Answer:

number of cubes in base layer is 6



Question 85.

In the above figure, if only shaded cubes are visible from the top, draw the base layer.


Answer:

The figure below is top view of only shaded cubes. The base layer is not seen from top.



Question 86.

How many faces, edges and vertices does a pyramid have with n sided polygon as its base?


Answer:

Faces = n + 1,vertices = n + 1,edges = 2n

Explanation: in a pyramid ,the number of faces is 1 more than the number of sides of the polygon base i.e faces = n + 1


Also, the number of vertices is 1 more than the number of sides of the polygon base i.e. vertices = n + 1


Also the no of edges of pyramid is 2 times the no of sides of polygon



Question 87.

Draw a figure that represents your mathematics textbook. What is the name of this figure? Is it is a Prism?


Answer:

The book is like the shape of a cuboids. Cuboids is like rectangular Prism



Question 88.

In the given figures, identify the different shapes involved.



Answer:

In the first figure hemisphere is mounted on the cylinder. In the second figure the hexagonal prism is mounted with a cone



Question 89.

What figure is formed if only the height of a cube increased or decreased?


Answer:

If We increase height of cube


If We decrease the height of cube




Question 90.

Use isometric dot paper to draw each figure?

(a) A tetrahedron

(b) A rectangular prism with length 4 units, width 2 units and height 2 units.


Answer:

(a)


(b)



Question 91.

Identify the nets given below and mention the name of the corresponding solid in the space provided.



Answer:



Question 92.

Draw a map of your school playground. Mark all necessary places like 2 library, Playground, Medical Room, Classrooms, Assembly area, etc.


Answer:




Question 93.

Refer to the given map to answer the following questions.



(a) What is the built-up area of Govt. Model School I?

(b) Name the schools shown in the picture.

(c) Which park is nearest to the dispensary?

(d) To which block does the main market belong?

(e) How many parks have been represented in the map?


Answer:

(a)The built-up area of Govt. model School I = 2.5acre

(b)Two schools shown in picture Govt model School I &II


(c)Park A is nearest to the dispensary


(d)The main market belongs to block A


(e)6 parks have been represented in the map



Question 94.

Look at the map given below.

Answer the following questions.

(a) Which two hospitals are opposite to each other?

(b) A person residing at Niti Bagh has to go to Chirag Delhi after dropping her daughter at Asiad Tower. Mention the important landmarks he will pass alongwith the roads taken.

(c) Name of which road is similar to the name of some month.



Answer:

The map is not sufficient to answer the question



Question 95.

Look at the map given below :



Now answer the following questions.

(a) Name the roads that meet at round about.

(b) What is the address of the stadium?

(c) On which road is the Police Station situated?

(d) If Ritika stays adjacent to bank and you have to send her a card. What address will you write?

(e) Which sector has maximum number of houses?

(f) In which sector is Fire Station located?

(g) In the map, how many sectors have been shown?


Answer:

(a)Flower road, Khel marg,mall road and sneha marg road meet at round

(b)The address of the Stadium sector27,B.Town,India.


(c)The police station is situated on sneha marg


(d)Aneha address H.N-1 Nr.Bank 1(A)


(e)Sector 27 has the maximum no of house


(f)Fire station is located in sector 26


(g)In the map, four sectors have been shown.



Question 96.

A photographer uses a computer program to enlarge a photograph. What is the scale according to which the width has enlarged?



Answer:

Width before editing the photograph = 2 units

Width after editing the photograph = 4 units


So, Scale =



Question 97.

The side of a square board is 50 cm. A student has to draw its image in her notebook. If the drawing of the square board in the notebook has perimeter of 40 cm, then by which scale the figure has been drawn?


Answer:

Given, the side of a square board is = 50cm.

So, perimeter of the square board = cm.


On drawing in the notebook, the perimeter of a square board = 40cm.


Scale



Question 98.

The distance between school and house of a girl is given by 5 cm in a picture, using the scale 1 cm : 5 km. Find the actual distance between the two places?


Answer:

Given Scale = 1cm:5km i.e. 1cm in picture = 5km of actual distance

So, 5cm in picture = 5*5 km of actual distance


Hence, the actual distance between the two places is 25 km.


So,5cm represent = distance



Question 99.

Use a ruler to measure the distance in cm between the places joined by dotted lines. If the map has been drawn using the scale 1 cm : 10 km, find the actual distances between

(1) School and Library

(2) College and Complex

(3) House and School



Answer:

Given scale is 1cm:10km i.e.1cm in a picture = 10km of actual distance

(a)The distance between the school and library in the picture = 6cm


Hence, the actual distance between the school and library =


(b)Distance between the college and complex in the picture = 2cm.


Actual distance between the college and complex


(c)Distance between the school and house in the picture = 3.5c.m = 3.5*10 = 35km



Question 100.

The actual length of a painting was 2 m. What is its length in the photograph if the scale used is 1 mm : 20 cm.



Answer:

The actual length of the painting 2m or 200c.m

Scale used in the painting = 1mm = 20cm


Hence, the length of painting in photograph = scale*Actual size =



Question 101.

Find the scale.

(a) Actual size 12 m

Drawing size 3 cm

(b) Actual size 45 feet

Drawing size 5 inches


Answer:

(a)Scale =

(b)Scale =



Question 102.

In a town, an ice cream parlour has displayed an ice cream sculpture of height 360 cm. The parlour claims that these ice creams and the sculpture are in the scale 1:30. What is the height of the ice creams served?


Answer:

Given height of ice cream sculpture = 360cm

Scale used for ice cream sculpture = 1:30


The height of ice-cream served =


Hence, the height of the ice-cream served is = 12cm