Question

What is the sum of first $20$ natural numbers?

Answer 1

Find the sum of first $20$ natural numbers

The sum of first $n$ natural numbers is $\frac{n\left(n+1\right)}{2}$.

The value of $n$ is $20$.

The sum of first $20$ natural numbers is $\frac{20\left(20+1\right)}{2}$

$$\begin{gathered} =10\times 21 \\ =210 \end{gathered}$$

Hence the sum of first $20$ natural numbers is $210$.