# Number combinations ...

Printable View

• March 26th 2008, 05:42 PM
GodKefka
Number combinations ...
So... Let's say we have the numbers :

01 02 03 04 05
06 07 08 09 10
11 12 13 14 15
16 17 18 19 20
21 22 23 24 25

If you need to choose 15 of them , I would like to know what's all the possible combinations .
• March 26th 2008, 05:50 PM
galactus
How many ways to choose 15 out of 25 numbers?.

C(25,15)=3,268,760
• March 26th 2008, 06:24 PM
GodKefka
well... ok, but how to use this formula ?
• March 27th 2008, 04:56 AM
galactus
Most calculators do combinations. That's what I used to do this one.

The formula is $C(n,k)=\frac{n!}{(n-k)!k!}$

Do you know what a factorial is?. That's what the exclamation points are.
• March 27th 2008, 11:00 AM
GodKefka
But I mean all possible combinations, without repeating them in a different order.