1.

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

Answer»

(C) 11 1/3

Explanation:

We know that,

Average of a data = sum of total observations / total number of observations

According to the question

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

(5x +15)/5 = 9

x + 3 = 9

x = 6

Now, the terms become

6, 6 + 3, 6 + 5, 6 + 7, 6 + 10 = 6, 9, 11, 13, 16

So, the mean of the last three observations = ( 11 + 13 + 16)/3

= 40/3

= 11 1/3

Hence, option (C) is the correct answer.


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