Question 696551
how many ways can i choose a set of 4 ties to take with me on a trip, if i have 11 different ties to choose from
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11*10*9*8 = 7920
but, choosing ties A, B, C & D is the same as A, C, B & D so it's 
7920/(4*3*2*1) = 330
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= 11!/((11 - 4)!*4!)