There is a story about the 7-year-old, German, mathematician Carl Friedrich Gauss. He responded to his teacher, Büttner's, request to sum the first 100 counting numbers (1 to 100). While his classmates toiled, Carl wrote a single number and handed it in. He was correct.

*Gauss on the old Deutsche Mark*

When asked how he did it, he explained that there were 50 pairs of numbers adding to 101. So, the sum must be 50 x 101 = 5050.

Here's he formula: **(n*(n+1))/2**

That version requires an even quantity and the first integer is 1.

For example: start easy and ask yourself:

**1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = ? **

Here's Gauss applied:

**[1 + 10 = 11]****[2 + 9 = 11]****[3 + 8 = 11]****[4 + 7 = 11]****[5 + 6 = 11]**

So, it's 11 five times; that's **55**, right? Check a calculator.

This simple formula has saved me lots of time.

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