Discussion Forum



1)

If the mean of 5 observations x, x + 2, x + 4, x + 6 and x + 8 is 11, then the mean of the last three observations is :


A) 11

B) 13

C) 15

D) 17

Answer:

Option B

Explanation:

We have $[\frac{x+(x+2)+(x+4)+(x+6)+(x+8)}{5}]=11$
5x+20 = 55
x= 7
So the numbers are 7,9,11,13,15
Required mean = $\frac{11+13+15}{3}=\frac{39}{3}=13$