Question

If the average of 5 observations $x,x+2,x+4,x+6$ and $x+8$ is $11$, then what is the average of the last three observations?

• A. $13$
• B. $15$
• C. $45$
• D. $61$

Answer 1

Answer: (A)

$13$

As per the given conditions, $\frac{x+x+2+x+4+x+6+x+8}{5}=11⟹5x+20=55⟹x+4=11⟹x=7$

Average of last three observations is $\frac{x+4+x+6+x+8}{3}=\frac{3x+18}{3}=x+6=13$