#2**+10 **

There is a "formula" for this. But notice when we add the first number, 1, and the last number, 100, we get 101. And addnig the next-to-the-last number, 99, and the second number, 2, we also get 101. And, continuing in this manner, we have 50 pairs of numbers that each add to 101. Therefore, 50 * 101 = 5050.

CPhill
Aug 22, 2014

#1**+10 **

You can think of it like this

0, 1, 2, ......................49

100,99,98,........................51

--------------------------------add

100+100+100..................100 , The only missing number is 50

So answer must be 100*50+50=5050

Melody
Aug 22, 2014

#2**+10 **

Best Answer

There is a "formula" for this. But notice when we add the first number, 1, and the last number, 100, we get 101. And addnig the next-to-the-last number, 99, and the second number, 2, we also get 101. And, continuing in this manner, we have 50 pairs of numbers that each add to 101. Therefore, 50 * 101 = 5050.

CPhill
Aug 22, 2014