Consider the letters A,B,C, and D. a) List all the different 2-letter permutations of these 4 letters. b) List all the different 2-letter combinations of these 4 letters. c) How is the number of 2-letter permutations related to the number of 2-letter combinations? Explain.
Consider the letters A,B,C, and D. a) List all the different 2-letter permutations of these 4 letters. b) List
a) There are 4!/(4-2)! = 12 permutations. Remember that with permutations, order matters.
AB
AC
AD
BA
BC
BD
CA
CB
CD
DA
DB
DC
b) There are 4!/(2!2!) = 6 combinations. Remember that with combinations, order does not matter.
AB
AC
AD
BC
BD
CB
CD
c. There are two times as many permutations as there are combinations in this example. That is because if you take any combination, then there are 2! = 2 ways to arrange them into different permutations.
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