What’s the sum of the numbers 1 to 100

Remark

You can use a formula to get the right answer. Otherwise you will use a lot of paper adding 100 numbers together.

Givens

A = 1

L = 100

n = 100 numbers to be added together. There are 100 numbers between 1 and 100 numbers inclusive.

Formula

Sum = (A + L)*n/2

Solution

Sum = (1 + 100)*100/2     Substitute in the givens. Add what is inside the brackets

Sum = (101) * 100 / 2       Divide by 2

Sum = 101* 50                  Multiply

Sum = 5050                     Answer