C(13,5) - C(8,5)

how do you solve c(13,5)-C(8,5)
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1 Answer

I presume that C is the combination function nCr.
The question means the number of combinations of 5 objects out of 13 less the number of combinations of 5 object out of 8.
C(13,5)=1,287 and C(8,5)=56, so 1287-56=1231.
Expanding the functions and the expression: (13*12*11*10*9/5*4*3*2*1)-(8*7*6*5*4/5*4*3*2*1)=147720/120=1231.
by Top Rated User (1.2m points)

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