Combination Formula

A formula for the number of possible combinations of r objects from a set of n objects. This is written in any of the ways shown below.

All forms are read aloud "n choose r."

Formula:
	Note: , where nPr is the formula for permutations of n objects taken r at a time.
Example:	How many different committees of 4 students can be chosen from a group of 15?
Answer:	There are possible combinations of 4 students from a set of 15.
	There are 1365 different committees.