Question

If the mean of five observations x, x + 2, x + 4, x + 6, x + 8, is 11, then the mean of first three observations is

A. 9

B. 11

C. 13

D. None of these

Answer 1

Correct answer is C.

First, you need to solve for x:

\(\frac{x+x+2+x+4+x+6+x+8}{5}=11\)

x + x + 2 + x + 4 + x + 6 + x + 8 = 55

5x + 20 = 55

5x = 35

x = 7

Now, substitute for x in each of the last three terms:

x + 4 + x + 6 + x + 8

(7 + 4) + (7 + 6) + (7 + 8)

(11) + (13) + (15)

\(\frac{39}{3} = 13\)

The mean is 13