Question 187350
How many different committees of 4 each can be chosen from a class of 15 members? 
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The 1st choice is 1 of 15, the 2nd 1 of 14, 13, 12.
15*14*13*12 = 32760
But, choosing ABCD is the same as ADCB or ACBD, etc, so you have to divide by 4*3*2*1, which is 24
32760/24 = 1365 possibilities.
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This is 15!/((15-4)!*4!)
! is factorial, and it's on most calculators.