Question

The mean of $1,2,3,\cdots (n+1)is\frac{6n}{11}$, then the value of n equals

• A. $20$
• B. $22$
• C. $18$
• D. $11$

Answer 1

The correct option is B $22$

We have, mean $=\frac{1+2+3+.............+(n+1)}{n+1}=\frac{6n}{11}$ (given)

$\frac{(n+1)\left(\right\{n+1\}+1)}{2(n+1)}=\frac{n+2}{2}=\frac{6n}{11}\Rightarrow 11n+22=12n\Rightarrow n=22$