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Q11: If a code word is defined to be a sequence of different [#permalink]
02 Jul 2007, 12:00
If a code word is defined to be a sequence of different letters chosen from the 10 letters A, B, C, D, E, F, G, H, I, and J, what is the ratio of the number of 5-letter code words to the number of 4-letter code words?