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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.

 

See also

Permutation, binomial coefficient, factorial

 


  this page updated 27-aug-12
Mathwords: Terms and Formulas from Algebra I to Calculus
written, illustrated, and webmastered by Bruce Simmons
NCTM Web Bytes December 2004 Web Bytes March 2005 Web Bytes