Question

If the mean of five observations $x,x+2,x+4,x+6$ and $x+8$ is 11, then the mean of last three obsevations is

• A. $11$
• B. $13$
• C. $15$
• D. $17$

Answer 1

The correct option is B $13$

Given observations $x,x+2,x+4,x+6,x+8$
$\because \frac{x+(x+2)+(x+4)+(x+6)+(x+8)}{5}=11$
$\Rightarrow \frac{5x+20}{5}=11$
$\Rightarrow x=7$
So, the observations are $7,9,11,13,15$
Req. mean $=\frac{11+13+15}{3}=13$