The average of the squares of first ten natural numbers is-

Answer: Option D

As we know that average of square of "n" natural number is
$$\begin{array}{rl}& =\frac{n\left(n+1\right)\left(2n+1\right)}{6n}\\ & =\frac{\left(n+1\right)\left(2n+1\right)}{6}\end{array}$$
According to the question,
Average of square of first ten natural number is
$$\begin{array}{rl}& =\frac{\left(10+1\right)\left(20+1\right)}{6}\\ & =\frac{11\times 21}{6}\\ & =38.5\end{array}$$