How many unique combinations of 5 items be made from a pool of 11 items? And how do I calculate this? I'm assuming there is some relationship w/ factorial involved, but I'm too stupid to work it out.
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Anonymous2011-01-16 23:37
You're thinking of nPr.
nPr means out of n population choose r elements and count mutations. That is, choose r elements from n and give the total numbers of possibles orders there are.
nPr is equal to n!/(n-r)!.
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Anonymous2011-01-17 8:45
NPR is National Public Radio, you guys!
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Anonymous2011-01-18 21:23
I think he wants nCr (aka the binomial coefficient).
nCr = n!/(r!(n-r!))
so in your the case, you want 11C5 = 11!/(5!*6!) = 462
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Anonymous2011-01-18 21:24
lol, I just realized he asked this 2 days ago...
Traffic here is less than I expected...
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Anonymous2011-01-19 17:47
>>4
You mistyped the nCr formula.
It's n!/(r!(n-r)!)
You did the work correctly, but I'm just clarifying in case someone looks at the formula you typed and gets confused.