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 [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 = 11+13+153=393=13