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Tricky probability question

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Tricky probability question

by pakaskwa » Wed Mar 04, 2009 10:27 pm
3 different letters to be placed into 4 different mail boxes. How many possible ways are there to place the letters into different mail boxes?
A. 4P3
B. 4C3
C. 3^4
D. 4^3
5. 3x4

What's the answer?
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by Feep » Thu Mar 05, 2009 12:06 am
4^3.

Unlike many probability questions on these tests, in this case, each letter is completely independent of the other letters. This is unlike, say, a seating arrangement, since if one seat is filled, the seat is no longer an option for the others.

Since each letter can go into one of the four mailboxes, there are 4 * 4 * 4 possibilities. So, 4^3.

You should probably at least understand the meaning of "4 pick 3" and "4 choose 3", though. They pop up occasionally.
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Master | Next Rank: 500 Posts
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by pakaskwa » Thu Mar 05, 2009 12:12 am
Thanks! That makes sense.
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