# SELINA Solutions for Class 9 Maths Chapter 19 - Mean and Median (For Ungrouped Data Only)

Page / Exercise

## Chapter 19 - Mean and Median (For Ungrouped Data Only) Exercise Ex. 19(A)

Solution 1

The numbers given are The mean of the given numbers will be Solution 2

The first six natural numbers are The mean of first six natural numbers  Solution 3

The first ten odd natural numbers are The mean of first ten odd numbers Solution 4

The all factors of 10 are The mean of all factors of 10 are Solution 5

The given values are The mean of the values are Solution 6

(i)The given numbers are  (ii) The value of We know that Here Therefore    Solution 7

Given that the mean of 15 observations is 32

(i)resulting mean increased by 3

=32 + 3

=35

(ii)resulting mean decreased by 7

=32 - 7

= 25

(iii)resulting mean multiplied by 2

=32*2

=64

(iv)resulting mean divide by 0.5 (v)resulting mean increased by 60% (vi)resulting mean decreased by 20% Solution 8

Given the mean of 5 numbers is 18

Total sum of 5 numbers

=18*5

=90

On excluding an observation, the mean of remaining 4 observation is 16

=16*4

=64

Therefore sum of remaining 4 observations total of 5 observations-total of 4 observations

= 90 - 64

= 26

Solution 9

(i)Given that the mean of observations x, x + 2, x + 4, x + 6 and x + 8 is 11

Mean=  (ii)The mean of first three observations are Solution 10

Given the mean of 100 observations is 40. Incorrect value of x=4000

Correct value of x=Incorrect value of x-Incorrect observation + correct observation

=4000-83+53

=3970

Correct mean Solution 11

Given that the mean of 200 items was 50. Incorrect value of Correct value of Correct mean Solution 12 Solution 13 Solution 14 Solution 15 Solution 16

Total number of tests = 8

Average score of A = 25

Let the score of 8th test be x.

Then, total score of 8 tests = 29 + 26 + 18 + 20 + 27 + 24 + 29 + x

Now, we have Thus, A scored 27 marks in the eights test.

## Chapter 19 - Mean and Median (For Ungrouped Data Only) Exercise Ex. 19(B)

Solution 1

(i)Firstly arrange the numbers in ascending order Now since

n=9(odd)

Therefore Median Thus the median is (ii)

Firstly arrange the numbers in ascending order

241, 243, 257, 258, 261, 271, 292, 299, 327, 347, 350

Now since n=11(Odd) (iii) Firstly arrange the numbers in ascending order Now since n=10(even)  Thus the median is (iv) Firstly arrange the numbers in ascending order

173,185,189,194,194,200,204,208,220,223 Thus the median is 197

Solution 2

Given numbers are 34, 37, 53, 55, x, x+2, 77, 83, 89, 100

Here n = 10(even) Solution 3

For any given set of data, the median is the value of its middle term.

Here, total observations = n = 10 (even)

If n is even, we have Thus, for n = 10, we have Hence, if 7th number is diminished by 8, there is no change in the median value.

Solution 4

Here, total observations = n = 10 (even)

Thus, we have According to given information, data in ascending order is as follows:

 1st Term 2nd Term 3rd Term 4th Term 5th Term 6th Term 7th Term 8th Term 9th Term 10th Term Marks Less than 30 35 40 48 66 More than 75 Hence, the median score of the whole group is 44.

Solution 5 ## Chapter 19 - Mean and Median (For Ungrouped Data Only) Exercise Ex. 19(C)

Solution 1 (i) Multiplied by 3 (ii) Divided by 2 (iii) multiplied by 3 and then divided by 2 (iv) increased by 25% (v) decreased by 40% Solution 2 Solution 3 Solution 4 Solution 5 Solution 6 Solution 7 (i)

Let us tabulate the observations and their deviations from the mean (ii) Solution 8 Let us rewrite the given data in ascending order:

Thus, we have

35, 48, 51, 52, 63, 64, 71, 76, 92

There are 9 observations, which is odd. If 51 is replaced by 66, the new set of data in ascending order is:

35, 48, 52, 63, 64, 66, 71, 76, 92 Solution 9 Solution 10 Therefore, the data set is:

1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, 72 Solution 11

Total number of students = 60

Mean weight of 60 students = 40

Let the number of boys = x

Then, number of girls = 60 - x Hence, the number of boys is 30 and the number of girls is also 30.

Solution 12

Mean of n numbers = A Solution 13

Total number of players in each team = 7 Thus, team A has greater average height.

Median of team A:

Arranging heights in ascending order, we get

175, 176, 178, 180, 181, 187, 190

Total number of observations = n = 7 (odd) Median of team B:

Arranging heights in ascending order, we get

174, 175, 177, 178, 179, 185, 190

Total number of observations = n = 7 (odd) ### STUDY RESOURCES

REGISTERED OFFICE : First Floor, Empire Complex, 414 Senapati Bapat Marg, Lower Parel, Mumbai - 400013, Maharashtra India.