**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 _{n}P_{r} 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 1365 different committees. |

**See also**

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