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niko
Aug 9, 2005, 05:36 PM
A contest consists of finding all of the code words that can be formed from the letters in the name "ATARI". Assume that the letter A can be used twice, but the others at most once.

a. How many five-letter words can be formed?

b. How many two-letter words can be formed?

c. How many words can be formed?

Answers
a. 60
b. 13
c. 170

Can anyone explain how to get these answers?

reinsuranc
Sep 7, 2005, 05:10 AM
If among n things, r1 are identical, and the rest are distinct, the number of permutations is n! / [(r1)! ]

a. Five letter words: = 5! / [2! ] = 60

You should be able to do the rest yourself.