Question

What is the sum of all numbers from $1$ to $99$?

Answer 1

Find the sum of all numbers from $1$ to $99$

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

The number of terms of the series is $99$.

The sum of the series is $\frac{99\left(99+1\right)}{2}$

$$\begin{gathered} =\frac{99\times 100}{2} \\ =99\times 50 \\ =4950 \end{gathered}$$

Hence, the sum of all numbers from $1$ to $99$ is $4950$.