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2012年新GRE数学考点指导——排列(1)

2012-11-02 

  Permutation of Objects

  The number of ways n distinct objects can be ordered is n!.

  Example:

  Number of ways 6 people can from a queue is 6!.

  Number of ways 5 different cars can be parked in 5 parking spaces is 5!.

  Remember: 

  This does not apply if there are identical objects or ordering does not matter.

  Permutation with Selection

  The number of ways n objects drawn from a collection of m distinct objects can be ordered is m!/(m-n)!.

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