The mean of the first ten even natural number is-

Answer: Option C

Required mean
$$\begin{array}{rl}& =\left(\frac{2+4+6+.....+20}{10}\right)\\ & =\frac{2\left(1+2+.....+10\right)}{10}\end{array}$$
$$=\left(\frac{1}{5}\times \frac{10\times 11}{2}\right)$$     $$\left[\because 1+2+3+...+n=\frac{n\left(n+1\right)}{2}\right]$$
$$=11$$