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  A set is a collection of objects or things. Each object in a set a member or element of that set.Size of a set is the number of members in the set.

  Example:

  The set of even numbers between 2 and 10 is of size 5:{2,4,6,8,10}.

  The set of primes between 2 and 10 is of size 4:{2,3,5,7}.

  Remember:

  Each member of set A belongs to A or is in the set A.

  A set can not have repeating member:{1,3,1,2}is not a set.

  Rearranging the order of the members does not change the set:{1,2,3}is same as{3,2,1}.

  Combinations

  Number of ways we can select n objects from a group of m distinct objects is m!/(n!*(m-n)!).

  Example:

  Number of possible ways to pick 4 oscar nominations from a list of 50 movies is 50!/(4!*(50-4)!)=50!/(4!*46!)=50*49*48*47/24=230300.

  Remember:

  This does not apply if there are identical objects.

  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.

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