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Statistics

Class 10th Mathematics Part 2 Kerala Board Solution

Questions Pg-249
Question 1.

The distance covered by an athlete in long jump practice are

6.10, 6.20, 6.18, 6.20, 6.25, 6.21, 6.15, 6.10

in metres. Find the mean and median. Why is it that there is not much difference between these?


Answer:

Mean is the average value


⇒ mean = 6.17


Median is the central value of a data set.


in this question we have 8 different number, and we have to find the median of these numbers.


Let’s write them in ascending order


6.10, 6.10, 6.15, 6.18, 6.20, 6.20, 6.21, 6.25


the two central values are and , i.e., 4th and 5th numbers


which are 6.18 and 6.20



⇒ median = 6.19


The mean and median are approximately same because all of the data are very near to each other.



Question 2.

The table below gives the rainfall during one week of September 2015 in various districts of Kerala.



Calculate the mean and median rainfall in Kerala during this week. Why is the median less than mean?


Answer:

let’s first write the data in ascending order

13.5,20.5,30.5,33.5,45.5,50.3,53.4,56.3,56.4,56.9,56.9,66.7,


70.6,89.0


there are total 14 values, so the two central values are 7th and 8th


term.



⇒ median = 54.85


mean is the average of all the values



⇒ 41.9



Question 3.

Prove that for a set of n numbers in arithmetic sequence, the mean and median are equal.


Answer:

let the first value be ‘a’ and the common difference be ‘d’.



Now we know that any kth term of the AP is given by


a + kd


n is the total number of terms, so the middle term would be .


and its value would be which is equal to the mean.




Questions Pg-252
Question 1.

15 households in a neighbourhood are sorted a according to their monthly income in the table below.



Calculate the median income.


Answer:

There are total 35 households.

the median monthly income of these houses will be Monthly Income of which is 18th term.



we can see that the 18th value is Rs. 6000 which is the also the monthly income and 8 other households and the other 10 have low income than Rs.6000.


∴ median = Rs.6000



Question 2.

The table below shows the workers in a factory sorted according to their daily wages:



Calculate the median daily wage


Answer:


total no. of workers = 32


the median would be the wage of = mean of 16th and 17th worker’s wage


⇒ In this question both the 16th and 17th worker have a wage of Rs. 700.


∴ median = Rs. 700



Question 3.

The table below gives the number of babies born in a hospital during a week, sorted according to their birth weight.



Calculate the median birth-weight.


Answer:


Sol. total no. of babies = 70


the median weight of babies would be the average weight of 35th and 36th baby.


both babies are having a weight of 3.000 kg


∴ the median weight of all the babies = 3.000 kg




Questions Pg-257
Question 1.

Some households in a locality are sorted according to their electricity usage and given in the table below:



Calculate the median usage.


Answer:


total number of households = 35


∴ the median is the usage of 18th household.


which lies between 110-120 and in this range there are 8 households.


let’s assume a uniform distribution.


i.e., 14th household’s usage is 110 and 15th household’s usage is 110 +


=


⇒ usage of 18th household =


⇒ usage of 18th household = 115


∴ 115 is the median value



Question 2.

The table below shows children in a class sorted according to their marks in a maths exam:



Calculate the median mark.


Answer:


total no. of children = 40


∴ the median is the mean of marks of 20th and 21st child.


both lies in the range of 20-30.


let’s assume a uniform distribution of marks.


i.e., 14th child has 20 marks and 15th child has 20 + marks.


⇒ marks of 15th child =


⇒ marks of 20th child =


⇒ marks of 20th child = 25


also, marks of 21st child =


median =


median =



Question 3.

The income tax paid by the workers in an office is shown below:



Calculate the median tax paid.


Answer:


the total number of workers = 90


⇒ median is the mean of 45th and 46th worker’s Income tax


both lies in the range of 4000-5000


let’s assume an equal distribution


33rd worker → 4000


34th worker → 4000 +


45th worker → 4000 + =


45th worker → 4000 + =


median =


⇒ median =