Question

If the mean of 1, 2, 3,..........,n is $\frac{6n}{11}$, then n is

• A. 10
• B. 12
• C. 11
• D. 13

Answer 1

The correct option is C

11

By the given condition $\frac{n(n+1)}{2n}=\frac{6n}{11}$
$\Rightarrow 11n^2+11n=12n\Rightarrow n^2=11n\Rightarrow n=11[\because n\ne 0]$