How to Add Consecutive Numbers

How to Add a Consecutive Series of Numbers in Your Head - wikiHow

* Think of the first and last number as a "stacks" that you add together. The second number and the second-to-last number will also equal the same sum.
To add 1-10:
10 + 1 = 11

Then divide the last number in sequence by two
10/2 = 5

Take these two numbers and multiply them to get the answer.

= 11 x 5
= 55

Adding 1-100
1 + 100 = 101 is the same as 2 + 99 = 101

- Add the first and last number together in the sequence.
- Divide the last number by two

1-100
101 x 50 sets = 5050

1-1,000
1001 x 500 = 500,500

1-1,000,000
1,000,0001 x 500,000 = 500,000,500,000 (500 Billion, 500 thousand)

Math Formula:
Here's another simple way to sum up a series of number. Use the mathmatical formula sum(n) = ( n * (n+1) ) / 2 - Check - This will work only if you want to add numbers starting from 1 and upto n.