Warning: The following may prove educational Adding up numbers from 1 to N is easy with a computer. Try doing it in your head is a little more tricky.

For instance 1+2+3+4=10. (that would be the pins at the end of a bowling lane). Or 1+2+3+4+5+6 = 21, which is the sum of "eyes" on a die. So what is the sum of the numbers from 1 to 100?

The story I was told, was of a young German kid, whose teacher wanted a little peace and quiet, so he asked the class to perform this addition. Gauss, as he was called, ansvered the question a few seconds later: 5050

The idea is the following: Adding all the numbers from 1 to 100 is equal to doing it twice and then halving the result. Due to the associative law, the order of which you count the numbers is independent of the end result, so if you choose to add up in this order: 1+100+2+99+3+98+ ... + 99+2+100+1 , you would end up with (1+100)+(2+99)+..etc. or 100 paranthesis adding up to 101. The end result halved is 101*100/2 = 101*50 = 5050. In general notation: 1+..+N = N*(N+1)/2.

I've been doing pushups this month. I started with one on May 1st, two on the 2nd and so forth. Today I reached number 300 and on May 31st I'll add four to my regular program to reach en even ... how many :oP