SELINA Solutions for Class 9 Maths Chapter 19  Mean and Median (For Ungrouped Data Only)
Chapter 19  Mean and Median (For Ungrouped Data Only) Exercise Ex. 19(A)
The numbers given are _{}
The mean of the given numbers will be
_{}
The first six natural numbers are _{}
The mean of first six natural numbers
_{}
_{}
The first ten odd natural numbers are _{}
The mean of first ten odd numbers
_{}
The all factors of 10_{ }are _{}
The mean of all factors of 10 are
_{}
The given values are _{}
The mean of the values are
_{}
(i)The given numbers are_{}
_{}
(ii) The value of _{}
We know that
_{}
Here
_{}
Therefore
_{}
_{}_{}
_{}
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%
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 observationstotal of 4 observations
= 90  64
= 26
(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
_{}
Given the mean of 100 observations is 40.
_{}
Incorrect value of x=4000
Correct value of x=Incorrect value of xIncorrect observation + correct observation
=400083+53
=3970
Correct mean
_{}
Given that the mean of 200 items was 50.
_{}
Incorrect value of _{}
Correct value of
_{}
Correct mean
_{}
Total number of tests = 8
Average score of A = 25
Let the score of 8^{th} 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)
(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
Given numbers are 34, 37, 53, 55, x, x+2, 77, 83, 89, 100
Here n = 10(even)
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 7^{th} number is diminished by 8, there is no change in the median value.
Here, total observations = n = 10 (even)
Thus, we have
According to given information, data in ascending order is as follows:

1^{st} Term 
2^{nd} Term 
3^{rd} Term 
4^{th} Term 
5^{th} Term 
6^{th} Term 
7^{th} Term 
8^{th} Term 
9^{th} Term 
10^{th} Term 
Marks 
Less than 30 
35 
40 
48 
66 
More than 75 
Hence, the median score of the whole group is 44.
Chapter 19  Mean and Median (For Ungrouped Data Only) Exercise Ex. 19(C)
_{}
(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%
_{}
_{}
_{}
_{}
_{}
_{}
_{}
(i)
Let us tabulate the observations and their deviations from the mean
_{}
(ii)
_{}
_{}
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
_{}
_{}
_{}
Therefore, the data set is:
1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, 72
_{}
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.
Mean of n numbers = A
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)
Kindly Sign up for a personalised experience
 Ask Study Doubts
 Sample Papers
 Past Year Papers
 Textbook Solutions
Sign Up
Verify mobile number
Enter the OTP sent to your number
Change