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Exponents Of Real Numbers

Class 9th Mathematics RD Sharma Solution
Exercise 2.1
  1. Assuming that x, y, z are positive real numbers, simplify each of the following:…
  2. Simplify: (i) (16-1/5)5/2 (ii) cube root (343)^-2 (iii) (0.001)1/3 (iv) (25)^3/2…
  3. Prove that: (i) root 3 x 5^-3 / cube root 3^-1 root 5 x root [6] 3 x 5^6 = 3/5…
  4. If 27x = 9/3^x , find x.
  5. Find the values of x in each of the following: (i) 25x 2x = root [5] 2^20 (ii)…
Cce - Formative Assessment
  1. The value of {2-3(2-3)^3 }^3 isA. 5 B. 125 C. 1/5 D. -125
  2. Write (625)-1/4 in decimal form.
  3. State the product law of exponents.
  4. (256)0.16 (256)0.09A. 4 B. 16 C. 64 D. 256.25
  5. State the quotient law of exponents.
  6. If 102y = 25, then 10-y equalsA. - 1/5 B. 1/50 C. 1/625 D. 1/5
  7. State the power law of exponents.
  8. The value of x-yx-y when x = 2 and y = -2 isA. 18 B. -18 C. 14 D. -14…
  9. The product of the square root of x with the cube root of x isA. Cube root of the…
  10. For any positive real number x, find the value of
  11. For any positive real number x, write the value of
  12. If 9x+2 = 240 + 9x, then x =A. 0.5 B. 0.2 C. 0.4 D. 0.1
  13. Write the value of {5(81/3 + 271/3)^3 }1/4
  14. Simplify .
  15. The seventh root of x divided by the eighth root of x isA. x B. root [n]x C. root [13]x…
  16. The square root of 64 divided by the cube root of 64 isA. 64 B. 2 C. 1/2 D. 642/3…
  17. If (x-1)^3 = 8, what is the value of (x+1)^2
  18. Which of the following is (are) not equal to (5/6)^1/2^-1/4 ?A. (5/6)^3/1- B.…
  19. When simplified (x-1 + y-1)-1 is equal toA. xy B. x + y C. xy/x+y D. x+y/xy…
  20. If 2^4 4^2 = 16x, then find the value of x.
  21. If 3x-1=9 and 4y+2 = 64, What is the value of x/y .
  22. If 8x+1 = 64, what is the value of 32x+1?A. 1 B. 3 C. 9 D. 27
  23. Write the value of cube root 7 x cube root 49 .
  24. If 0 y x, which statement must be true?A. root x - root y = root x-y B. root x + root…
  25. Write (1/9)^-1/2 (64)-1/3 as a rational number.
  26. If x is a positive real number and x^2 = 2, then x^3 =A. root 2 B. 2 root 2 C. 3 root…
  27. Write the value of cube root 125 x 27 .
  28. If (2^3)^2 = 4x, then 3x =A. 3 B. 6 C. 9 D. 27
  29. If 10x = 64, what is the value of 10^x-1 ?A. 18B. 42C. 80D. 81
  30. If = 8x-1 and x 0, then x =A. root 2/4 B. 2 root 2 C. 4 D. 64
  31. If g = t2/3 + 4t-1/2, what is the value of g when t = 64?A. 31/2 B. 33/2 C. 16 D.…
  32. If x-2 = 64, then x1/3 + x^0 =A. 2 B. 3 C. 3/2 D. 2/3
  33. If 4x - 4x-1 = 24, then (2x)x equalsA. 5 root 5 B. root 5 C. 25 root 5 D. 125…
  34. When simplified (- 1/27)^-1/3 isA. 9 B. -9 C. y/bar 9 D. - y/9
  35. Which one of the following is not equal to (cube root 9)^-1/2 ?A. (cube root 2)^-1/2…
  36. Which one of the following is not equal to (100/9)^-3/2 ?A. (100/9)^3/2 B.…
  37. When simplified (256)^- (20/2) isA. 8 B. y/8 C. 2 D. 1/2
  38. 5^n+2 - 6 x 5^n+1/13 x 5^n - 2 x 5^n+1 is equal toA. 5/3 B. - 5/3 C. 3/5 D. - 3/5…
  39. If a, b, c are positive real numbers, then is equal toA. 1 B. abc C. root 3bc D. y/3bc…
  40. If 3^2x-3/225 = 5^2/5^x , then x =A. 2 B. 3 C. 5 D. 4
  41. If (2/3)^2 (3/2)^2/2 = 81/16 , then x=A. 2 B. 3 C. 4 D. 1
  42. The value of 8^-4/3+2^-2^1/2 isA. 1/2 B. 2 C. y/4 D. 4
  43. If a, b, c are positive real numbers, then is equal toA. 5a^2 bc^2 B. 25ab^2 c C. 5a^3…
  44. The value of 64-1/3 (641/3 - 642/3), isA. 1 B. 1/3 C. -3 D. -2
  45. If root 5^n = 125, then 5 root 64 =A. 25 B. 1/125 C. 625 D. 10
  46. If (16)2x+3 =(64)x+3, then 42x-2 =A. 64 B. 256 C. 32 D. 512
  47. If a, m, n are positive integers, then m root n root a^mm is equal toA. amn B. a C.…
  48. If 2-m 1/2^m = 1/4 , then 1/14 (4m^1/2 + (1/5^pi)^-1] is equal toA. 1/2 B. 2 C. 4 D. -…
  49. If x = 2 and y = 4, then (x/y)^x-y + (y/x)^y-x =A. 4 B. 8 C. 12 D. 2…
  50. The value of m for which [(1/7^2)^-2]^-1/3]^1/4 = 7m, isA. - 1/3 B. 1/4 C. -3 D. 2…
  51. If = 16,and a = 21/10, then =A. 2 B. 1/4 C. 9 D. 1/8
  52. The value of {(23+2^2)2/3+(140 - 19)1/2}^2 , isA. 196 B. 289 C. 324 D. 400…
  53. If root 2^n = 1024, then 3^2^2^-2 =A. 3 B. 9 C. 27 D. 81
  54. If 3^1x x 81^2 x 6561/3^2x = 3^7 , then x =A. 3 B. -3 C. 1/3 D. - 1/3…

Exercise 2.1
Question 1.

Assuming that x, y, z are positive real numbers, simplify each of the following:

(i) (ii) (iii) (x-2/3y-1/2)2 (iv) (v) (vi)


Answer:

(i) ( )5 = (1 / x3/2) 5

= (1 / x 3/2 × 5) = (1 / x 15/2)


(ii) (3 / y2) = (x3 / y2) 1/2


= x3 × 1/2 / y2 × 1/2


= x3/2 / y


(iii) 1 / (x2/3 y1/2)2


= 1 / (x2/3 × 2 y1/2 × 2)


= 1 / x4/3 y


(iv) (x1/2)-2/3 (y)2 / (xy-1/2)1/2


= x-1/3y2 / (x1/2y-1/2×1/2)


= (x-5/6) (y9/4)


= (y9/4) / (x5/6)


(v) (243x10 y5 z10) 1/5


= (35)1/5 x2yz2


= 3x2yz2


(vi) (y10 / x4)5/4


= y 10 × 5/4 / x4 × 5/4


= y25/2 / x5


Question 2.

Simplify:

(i) (16-1/5)5/2 (ii) (iii) (0.001)1/3 (iv) (v) (vi)


Answer:

(i)

We know for any non-zero number a,

(am)n = amn

So,

As we know 42 = 16

Therefore,

= 4-1

As we know for any non-zero number a,

a-1 = 1/a

So 4-1 = 1/4

(ii) [(343)-2]1/3


We know for any non-zero number a,

(am)n = amn

So,

As we know 73 = 343

Therefore,

= 7-2

As we know for any non-zero number a,

a-1 = 1/a

So 7-2= 1/72

= 1/49


(iii) ()1/3 = (1 / 103) 1/3


= = 0.1


(iv)

We know 25 = 52

243 = 35

16 = 24

8 = 23

So,

We know for any non-zero number a,

(am)n = amn

So,


(v)

We know that for any non-zero number a,

am ÷ an = am-n

So,

As we know for any non-zero number a,

a-1 = 1/a


(vi)
We know for any non-zero number a,

(am)n = amn

So,

We know for any non-zero number a,

am × an = am+n

= 25 × 7

= 175


Question 3.

Prove that:

(i)

(ii) 93/2 -3× 50 - = 15

(iii) -3×82/3 ×40+

(iv) = 10

(v) + (0.01)-1/2 – (27)2/3 =

(vi)

(vii)

(viii) = 28

(ix)


Answer:

(i) (31/2+1/6.5-3/2 +1) / (3-1/3.51/2)

=(32/3.5-1/2) / (3-1/3.51/2)


=(32/3 + 1/3) / (51/2 +1/2)


=3/5


(ii) (32 )3/2 -3.1 – (1/92)-1/2


= 33 -3 -9


=27 -3 -9


=27-12


=15


(iii) 2(-2)(-2) -3.82/3 +(3/4)-1


=24 -3.22 + 4/3


=16 -12 + 4/3


=16/3


(iv) [(2.31/3)/(2-1/5 52/5)] × (2-1/5.3)/ (34/3.57/5)


= 2.31/3 +1 -4/3 / 52/5-7/5


= 2.5


=10


(v) 1/2 + 1/(0.01)1/2 -32


=1/2 + 10 – 9


=1/2 + 1


=3/2


(vi) (2n + 2n-1)/ ) (2n+1 - 2n)


=2n(1 + 2-1 ) / 2n (2-1)


= [1 + (1/2)]/1


=1 + 1/2


=3/2


(vii) (125/64)2/3 + (625/256)1/4 + ( 5/4)


=(5/4)2 + 5/4 + 5/4


=25/16 + 5/4 + 5/4


=65/16


(viii) (3-3.62.7(2)1/2)/ (54/3.(15)-4/3‑.31/3) =28(2)1/2


(3-3.36.7(2)1/2)/ (54/3-4/3.(3)-1)


(3-2.36.7(2)1/2)/ (50)


1/9.36.7(2)1/2


28


(ix) {1- 1/0.1}/ { (3/8)-1(3/2)3 + (-1/3)-1


=1-10/{ (8/3)(3/2)3 + (-3)


=-9/(32-3)


= -3/2



Question 4.

If 27x =, find x.


Answer:

We have,

(27)x = 9 / 3x


(33)x = 32 / 3x


33x = 3 2 – x


3x = 2 – x {On equating exponents}


3x + x = 2


4x = 2


x = =


Hence, the value of x is



Question 5.

Find the values of x in each of the following:

(i) 25x÷ 2x =

(ii) (23)4 = (22)x

(iii)

(iv) 5x-2 × 32x-3 = 135

(v) 2x-5 × 5x-4 = 5

(vi) 2x-7 × 5x-4 = 1250


Answer:

(i) we have,

25x÷ 2x =


25x/2x = 220/5


25x-x = 24


4x = 4


x=1


(ii) We have,


(23)4 = (22)x


23.4 = 22.x


12 = 2x


X=6


(iii) We have,



52x-x/ 32x-x = ()3


5x/3x = ()3


()x = ()3


x=3


(iv) We have,


5x-2 × 32x-3 = 135


5x-2 × 32x-3 = 5


5x-2 × 32x-3 = 513


x-2 =1 ; 2x-3 =3


x=3 ; x= 3


(v) We have,


2x-5 × 5x-4 = 5


2x-5 × 5x-4 = 51 × 20


x-5=0 ; x-4 = 1


x= 4 ; x=1 +4 =5


(vi) We have,


2x-7 × 5x-4 = 1250


2x-7 × 5x-4 = 21 × 54


x – 7=1; x-4 = 4


x= 8; x= 4+4 = 8




Cce - Formative Assessment
Question 1.

The value of {2-3(2-3)3}3 is
A. 5

B. 125

C. 1/5

D. -125


Answer:

{2-3(2-3)3}3

= {2 – 3 (-1)3}3


= {2 + 3}3


= 53 = 125


Question 2.

Write (625)-1/4 in decimal form.


Answer:


= 0.2


Question 3.

State the product law of exponents.


Answer:

The product law of exponent states that while multiplying two parts having same base, you can add the exponents.



Question 4.

(256)0.16 × (256)0.09
A. 4

B. 16

C. 64

D. 256.25


Answer:

(256)0.16 × (256)0.09

= (256) 0.16 + 0.09


= (256) 0.25


= 44 × = 4


Question 5.

State the quotient law of exponents.


Answer:

The quotient law of exponent states that to divide two exponents with the same base, you keep the base and subtract the powers.



Question 6.

If 102y = 25, then 10-y equals
A.

B.

C.

D.


Answer:

102y = 25

= 10y = x


= x2 = 52


= x = 5


= 1/x = 10-y


= 1/5


Question 7.

State the power law of exponents.


Answer:

The power law of exponents states that:

(an)m = an.m


Example: (23)2 = 23.2


= 26 = 64



Question 8.

The value of x-yx-y when x = 2 and y = -2 is
A. 18

B. -18

C. 14

D. -14


Answer:

x – y x – y

= 2 – (-2)(2 + 2)


= 2 – 16 = - 14


Question 9.

The product of the square root of x with the cube root of x is
A. Cube root of the square root of x

B. Sixth root of the fifth power of x

C. Fifth root of the sixth power of x

D. Sixth root of x


Answer:

×

= x1/2 × x1/3


= x5/6


Question 10.

For any positive real number x, find the value of


Answer:

x(a – b) (a + b) × x(b – c) (b + c) × x(c – a) (c + a)

= xa.a - b.b × xb.b – c.c × xc.c – a.a


= xa.a – b.b + b.b – c.c + c.c – a.a


= xo = 1



Question 11.

For any positive real number x, write the value of


Answer:

(x)ab × 1/ab . (x)bc . 1/bc . xca . 1/ca

= x . x . x


= x3



Question 12.

If 9x+2 = 240 + 9x, then x =
A. 0.5

B. 0.2

C. 0.4

D. 0.1


Answer:

9x + 2 = 240 + 9x

9x × 92 = 240 + 9x


Let 9x = y


81y = 240 + y


80y = 240


y =


9x = 3


32x = 3


2x = 1


x = = 0.5


Question 13.

Write the value of {5(81/3 + 271/3)3}1/4


Answer:

{5(81/3 + 271/3)3}1/4

= {5 (2 + 3)3}1/4


= (54)1/4 = 5



Question 14.

Simplify .


Answer:





Question 15.

The seventh root of x divided by the eighth root of x is
A. x

B.

C.

D.


Answer:

x1/7 / x1/8

= (x)1/7 – 1/8


= (x)1/56


=


Question 16.

The square root of 64 divided by the cube root of 64 is
A. 64

B. 2

C.

D. 642/3


Answer:

As 64 can be written as 64 = 2×2×2×2×2×2
so 64 = 26
√64=√(26)=(26)1/2 = 23=8

=(26)1/3 = 22=4
= = 2


Question 17.

If (x-1)3 = 8, what is the value of (x+1)2


Answer:

(x – 1)3 = 8

x – 1 = 2


x = 3


(x + 1)2 = (3 + 1)2


= 42 = 16



Question 18.

Which of the following is (are) not equal to ?
A.

B.

C.

D.


Answer:


= 1 / {(5/6)1/5}1/5


= (5/6)-1/30


= (6/5)1/30


Question 19.

When simplified (x-1 + y-1)-1 is equal to
A. xy

B. x + y

C.

D.


Answer:

(x-1 + y-1)-1

= ( + ) -1


= () -1


= ()


Question 20.

If 24×42 = 16x, then find the value of x.


Answer:

24 × 24 = 16x

28 = 24 × x


x = 24 = 16



Question 21.

If 3x-1=9 and 4y+2 = 64, What is the value of .


Answer:

3x – 1 = 32

x – 1 = 2


x = 3


4y + 2 = 43


y + 2 = 3


y = 1


x / y = 3/1 = 3



Question 22.

If 8x+1 = 64, what is the value of 32x+1?
A. 1

B. 3

C. 9

D. 27


Answer:

8 x + 1 – 64

= 8 x + 1 = 82


On equating powers, we get


x + 1 = 2


x = 1


= 3 2x + 1


= 33 = 27


Question 23.

Write the value of .


Answer:


= (7 . 72)1/3


= (7)3×1/3


= 7



Question 24.

If 0 < y < x, which statement must be true?
A.

B.

C.

D.


Answer:

Since, it is the property of square roots.


Question 25.

Write × (64)-1/3 as a rational number.


Answer:

× (64)-1/3

= (32)1/2 × (1/43) -1/3


= 3 × 1/4 = 3/4



Question 26.

If x is a positive real number and x2 = 2, then x3 =
A.

B. 2

C. 3

D. 4


Answer:

x2 = 2

x =


x3 = (2)1/2 × 3


= 2


Question 27.

Write the value of.


Answer:


= (53 × 33)1/3


= 5 × 3


= 15



Question 28.

If (23)2 = 4x, then 3x =
A. 3

B. 6

C. 9

D. 27


Answer:

(23)2 = 22x

2x = 6


x = 3


Question 29.

If 10x = 64, what is the value of?
A. 18
B. 42
C. 80
D. 81


Answer:

can be written as: (10x)1/2 × 10

= (64)1/2 × 10

= 8 × 10

= 80


Question 30.

If = 8x-1 and x > 0, then x =
A.

B. 2

C. 4

D. 64


Answer:





Question 31.

If g = t2/3 + 4t-1/2, what is the value of g when t = 64?
A.

B.

C. 16

D.


Answer:

g = t2/3 + 4t-1/2

= (64)2/3 + 4 (64) -1/2


= [(64)1/3]3 + 4 () 1/2


= 42 + 4 ()


= 16 + =


Question 32.

If x-2 = 64, then x1/3 + x0 =
A. 2

B. 3

C. 3/2

D. 2/3


Answer:

()2 = (8)2

= 8


x =


x1/3 + xo


= ()1/3 + ()o


= + 1 =


Question 33.

If 4x – 4x-1 = 24, then (2x)x equals
A. 5

B.

C. 25

D. 125


Answer:

4x – 4x – 1 = 24

Let 4x = y


y - = 24


4y – y = 96


y = 32


4x = 32


22x = 25


(2x)x = (2 × )5/2


= (5)5/2 = 25


Question 34.

When simplified is
A. 9

B. -9

C.

D.


Answer:

(-27) 2/3

= (3)3 × 2/3


= 9


Question 35.

Which one of the following is not equal to ?
A.

B. 8-1/6

C.

D.


Answer:

1 / (8)-1/2 × 1/3

= 2-1/2


=


Question 36.

Which one of the following is not equal to ?
A.

B.

C.

D.


Answer:

1 / (100/9)3/2

= (10/3)-3/2 × 2


=


Question 37.

When simplified is
A. 8

B.

C. 2

D.


Answer:

1 / 2561/8

= 1/28 × 1/8


= 1/2


Question 38.

is equal to
A.

B.

C.

D.


Answer:

5n (25 – 30) / 5n (13 – 10)

= -5 / 3


Question 39.

If a, b, c are positive real numbers, then is equal to
A. 1

B. abc

C.

D.


Answer:

(b/a)1/2 × (c/b)1/2 × (a/c)1/2

= (b/a × c/b × a/c)1/2


= 1


Question 40.

If, then x =
A. 2

B. 3

C. 5

D. 4


Answer:

= 5x × 32x – 8 = 55 × 33

Comparing the coefficient of x we get,


= x = 5


Question 41.

If , then x=
A. 2

B. 3

C. 4

D. 1


Answer:

(3/2)-x (3/2)2x = (3/2)4

= (3/2)-x + 2x = (3/2)4


= -x + 2x = 4


= x = 4


Question 42.

The value of is
A.

B. 2

C.

D. 4


Answer:


= {2-4 2-2}1/2


= {1/16 × 22}1/2


=


Question 43.

If a, b, c are positive real numbers, then is equal to
A. 5a2bc2

B. 25ab2c

C. 5a3bc3

D. 125a2bc2


Answer:

(3125a10b5c10)1/5

= 5a2bc2


Question 44.

The value of 64-1/3 (641/3 – 642/3), is
A. 1

B.

C. -3

D. -2


Answer:

64-1/3 (641/3 – 642/3)

= 4-1 (4 – 42)


= (4 – 16)


= = -3


Question 45.

If = 125, then 5 =
A. 25

B.

C. 625

D. 10


Answer:

= 125

5n/2 = 53


n/2 = 3


n = 6


5 = 5 (64)1/6


= 5 (2)6/6 = 10


Question 46.

If (16)2x+3 =(64)x+3, then 42x-2 =
A. 64

B. 256

C. 32

D. 512


Answer:

44x + 6 = 4 3x + 9

= 4x + 6 = 3x + 9


= x = 3


42x – 2 = 44


= 256


Question 47.

If a, m, n are positive integers, then is equal to
A. amn

B. a

C. am/n

D. 1


Answer:

We know for any non-zero number a,

am × an = am+n

Again using (am)n = amn we get,

=a


Question 48.

If 2-m×, then is equal to
A.

B. 2

C. 4

D.


Answer:

2-m × 1 / 2m = 1/4

= 1/2m × 1/2m = 1/4


= 1/4m = 1/4


= m = 1


1/14 {(4m)1/2 + (1/5m)-1}


= 1/14 {2 + 5}


= 1/14 × 7


=


Question 49.

If x = 2 and y = 4, then +=
A. 4

B. 8

C. 12

D. 2


Answer:

(2/4) 2 – 4 + (4 / 2)4 – 2

= (1/2)-2 + 22


= 22 + 22


= 8


Question 50.

The value of m for which = 7m, is
A.

B.

C. -3

D. 2


Answer:

[{74}-1/3]1/4

= (1/74)1/3 × 1/4


= (1/7)1/3 = 7m


= 7 -1/3 = 7m


= m = -1/3


Question 51.

If = 16,and a = 21/10, then =
A. 2

B.

C. 9

D.


Answer:



2m + n - n + m = 24

22m = 24

2m = 4

m = 2

Also a = 21/10




= a2m + m + n - 2n - p + 2p

= a3m - n + p


Question 52.

The value of {(23+22)2/3+(140 – 19)1/2}2, is
A. 196

B. 289

C. 324

D. 400


Answer:


= {32 + 11}2


= (9 + 11)2


= (20)2 = 400


Question 53.

If = 1024, then=
A. 3

B. 9

C. 27

D. 81


Answer:

= 210

2n/2 = 210


= 10



= 32 (n / 4 – 4)


= 32 (20/4 – 4)


= 32 = 9


Question 54.

If = 37, then x =
A. 3

B. -3

C.

D.


Answer:

= 37

= 35x × 38 × 38/ 32x = 37


= 35x + 16 – 2x = 37


= 5x + 16 – 2x = 7


= 3x + 16 =7


= 3x = -9


x = -3