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drawing possibility..

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drawing possibility..

by ska7945 » Mon Aug 11, 2008 4:30 pm
6)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?

A. 5 to 4 B. 3 to 2 C. 2 to 1 D. 5 to 1 E. 6 to 1


explanation needed thx.

answer E
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by kris610 » Mon Aug 11, 2008 4:44 pm
If you are not familiar with Combinatorics:

The first letter may be selected in 10 ways. For each of the 10 possible ways, you may choose the second letter in 9 possible ways and so on.

So, the required ratio would be:

10*9*8*7*6:10*9*8*7, which would be 6:1
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