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Question 1 (nov.17th)

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Question 1 (nov.17th)

by bacali » Mon Nov 17, 2008 10:08 am
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


OA: E
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by bacali » Mon Nov 17, 2008 10:09 am
I don't get this. Wouldn't it just be 5!/4! as a ratio?? Please help.
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by dmateer25 » Mon Nov 17, 2008 11:49 am
For the five letter word

The first letter can be 10 different letters
The second letter can be 9 different letters
The third letter can be 8 different letters
The fourth letter can be 7 different letters
The fifth letter can be 6 different letters

10*9*8*7*6=30240

For the four letter word

The first letter can be 10 different letters
The second letter can be 9 different letters
The third letter can be 8 different letters
The fourth letter can be 7 different letters

10*9*8*7=5040


30240:5040 = 6:1
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