# Summing numbers 0 to 100

• Mar 22nd 2009, 01:38 PM
Jassim
Summing numbers 0 to 100
Suppose you have a list of numbers from zero to one hundred. How quickly can you add them all up without using a calculator?
• Mar 22nd 2009, 02:00 PM
running-gag
You can use Gauss method
$S=1 + 2 + 3 + \cdots + 98 + 99 + 100$
$S=100 + 99 + 98 + \cdots + 3 + 2 + 1$

$2S=101 + 101 + 101 + \cdots + 101 + 101 + 101$

2S is the sum of 100 terms equal to 101

Therefore $S=\frac{100\cdot101}{2}=5050$
• Mar 22nd 2009, 02:41 PM
Jassim
thx
thanks very much for your help
• Mar 23rd 2009, 06:21 AM
stapel