Posted by **Hannah** on Saturday, August 10, 2013 at 2:13am.

If I add all the numbers from 1-100 what do I get? This question has been confusing me for a while...

- Math -
**Sue**, Saturday, August 10, 2013 at 2:19am
901

- Math -
**Anonymous**, Saturday, August 10, 2013 at 2:26am
you get 5050

- Math -
**Aman**, Saturday, August 10, 2013 at 2:28am
5050

- Math -
**Jai**, Saturday, August 10, 2013 at 2:30am
The formula for calculating the sum of consecutive number is

S = n*(a1 + an) / 2

where

n = number of terms

a1 = first number

an = last number

Since it is from 1 to 100, n = 100. Substituting,

S = 100*(1+100)/2

S = 5050

Hope this helps~ :)

- Math -
**Steve**, Saturday, August 10, 2013 at 4:20am
You can also do it quickly as Gauss discovered when he was a child.

Consider all the numbers as if written in two lines.

1-50 ascending

100-51 descending

adding the two numbers that are in the same positions, each pair makes 101. There are 50 such pairs, so the sum is 5050.

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