SOLUTION: Four tennis players enter a tournament. How many different ways can the pairings be made for the first round games? (A) 3 (B) 6 (C) 8 (D) 12 (E) 24

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Question 288053: Four tennis players enter a tournament. How many different ways can the pairings be made for the first round games?
(A) 3 (B) 6 (C) 8 (D) 12 (E) 24

Answer by amnd(23) About Me  (Show Source):
You can put this solution on YOUR website!
The number of ways of partitioning a set of n objects into r cells with N1 elements in the first cell, N2 elements in the second, and so on until Nr is:
n%21%2FN1%21N2%21Nr%21
There are 4 tennis players, which makes 2 pairs (“cells”). Therefore, the solution would be:
4%2F2.2=4%21%2F2%212%21
4!/2!2! = 4.3.2!/2.1.2! = 12/2 = 6 possibilities (B)