What is the sum of all numbers from one to one hundred?

Answer 1

5050

1 + 2 + 3 + . . . . + 99 + 100 = ?

Arrange the numbers to add them like this:

(1 + 100) + (2 + 99) + (3 + 98) + . . . . + (50 + 51) = ?

If you notice every pair of numbers adds up to 101. There are 50

pairs of numbers, so the answer is 50*101 = 5050.

In general to find the sum of all the numbers from 1 to N:

1 + 2 + 3 + 4 + . . . . + N = (1 + N)*(N/2)

That is "1 plus N quantity times N divided by 2."

Hope this helps.