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August 25th, 2009, 12:44 AM   #1
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Permutation with variables & numbers

Hi. Not sure if this belongs here... I'm trying to find the number of different combinations with, say, 3 different groups. [A-Z(22)] [0-9(10)] and [0-9(10)]
I attempted to set up some type of factorial of this (didn't think the pascal triangle would help), but alas I'm too baked to actually write out the thousands of possible combinations (which explains why I'm on a math forum while I'm out of school asking about middle school caliber math)

there would be 6 different combinations w/ 1 letter ,n1, and n2 (a12 a21 1a2 12a 2a1 21a)

then theres the number of different combinations of numbers

10 ! 10 ! 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1
_______ =_______=______________________________ = 10 x 9 = 90
(10 - 2) ! 8 ! 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1

so w/ 90 different combinations of numbers to choose , 22 letters, and 6 possible places each can hold, would you just subtract 1 set for each multiplicity?
n1 n2 have 12 places for each letter

amidoinitrite? Thanks in advance.
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August 25th, 2009, 05:29 AM   #2
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Re: Permutation with variables & numbers

I don't understand what combinations you're allowing. You can choose from 22 (or 26?) letters, but can each slot hold a letter? Can they be repeated? Does order matter? what does "6 possible places each can hold" mean? Maybe an example would help.
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