Question

The arithmetic mean of 1, 2, 3, ... , n is

(a) $\frac{n+1}{2}$
(b) $\frac{n-1}{2}$
(c) $\frac{n}{2}$
(d) $\frac{n}{2}+1$

Answer 1

Arithmetic mean of 1, 2, 3, ... , n

$$\begin{gathered} =\frac{1+2+3+...+n}{n} \\ =\frac{{\displaystyle \frac{n\left(n+1\right)}{2}}}{n} \\ =\frac{n+1}{2} \end{gathered}$$

Hence, the correct option is (a).