Correct Answer: 25.5

Sum of first n natural numbers = \( \large\frac{n\left(n + 1\right)}{2} \)

So, average of first n natural numbers = \(\large n\left( n + 1 \right) \)= \( \large\frac{n + 1}{2} \)

Average = \( \large \left( \frac{50 + 1}{2} \right) = \frac{51}{2} = 25.5 \)