Question

What is 1 + 2 + 3 + ....... + 99 + 100 equal to? Also what is a quick method to solve this?

Answer 1

`5050.`

Explanation:

Observe that,

`1+2+3+4+...+50+51+...+97+98+99+100,`

`=(1+100)+(2+99)+(3+98)+(4+97)+...+(50+51),`

`=(101)+(101)+(101)+(101)+...+(101),......(50" terms)"`

`=101*50,`

`=5050.`