39th Problem

$\large \displaystyle \text{ Arithmetic mean for first 149 natural numbers } = \frac{1 + 2 + 3 + ........ + 149}{149}\\ \large \displaystyle = \frac{149 \times (149+1)}{2 \times 149} = \frac{150}{2} = \color{#20A900}{\boxed{75}}.$

Arithmetic mean of first 'n' natural numbers is = $\frac{n+1}{2}$

Then , it will be equal to $\frac{149+1}{2}$ = 75