The arithmetic mean of first 11 natural numbers is

A. 5

B. 5.5

C. 6.0

D. 6.5

Answer: Option C

Solution(By Examveda Team)

Required mean
$$\eqalign{ & = \left( {\frac{{1 + 2 + ..... + 11}}{{11}}} \right) \cr & = \left( {\frac{1}{{11}} \times \frac{{11 \times 12}}{2}} \right) \cr & = 6 \cr} $$
$$\left[ {\because 1 + 2 + ..... + n = \frac{{n\left( {n + 1} \right)}}{2}} \right]$$