If the mean of the observations : x, x + 3, x + 5, x + 7, x + 10 is 9, the mean of the last three observations is
a. 10 1/3
b. 10 2/3
c. 11 1/3
d. 11 2/3

Solution:

It is given that

Mean of observations x, x + 3, x + 5, x + 7, x + 10 is 9

We can write it as

(x + x + 3 + x + 5 + x + 7 + x + 10)/5 = 9

By further calculation

5x + 25 = 45

5x = 45 - 25

5x = 20

Dividing both sides by 5

x = 4

So the last three observations will be

x + 5 = 4 + 5 = 9

x + 7 = 4 + 7 = 11

x + 10 = 4 + 10 = 14

Mean of last three observations = (9 + 11 + 14)/3 = 34/3 = 11 1/3

Therefore, the mean of the last three observations is 11 1/3.

✦ Try This: If the mean of the observations : x + 2, x + 4, x + 6, x + 8, x + 10 is 4, the mean of the last three observations is

☛ Also Check: NCERT Solutions for Class 9 Maths Chapter 14

NCERT Exemplar Class 9 Maths Exercise 14.1 Problem 12

If the mean of the observations : x, x + 3, x + 5, x + 7, x + 10 is 9, the mean of the last three observations is a. 10 1/3, b. 10 2/3, c. 11 1/3, d. 11 2/3

Summary:

If the mean of the observations : x, x + 3, x + 5, x + 7, x + 10 is 9, the mean of the last three observations is 11 1/3

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