The formula for a combination of choosing

_{n}P_{r} = | n! |

(n - r)! |

where n is the number of items and r is the number of arrangements.

_{10}P_{6} = | 10! |

(10 - 6)! |

Remember from our factorial lesson that n! = n * (n - 1) * (n - 2) * .... * 2 * 1

n! = 10!

10! = 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1

10! = 3,628,800

(n - r)! = (10 - 6)!

(10 - 6)! = 4!

4! = 4 x 3 x 2 x 1

4! = 24

_{10}P_{6} = | 3,628,800 |

24 |