Re: Combinations
This is basic probability, pick up a high school probability maths book will explain everything.
But in essence, for JJ:
#combinations = 4 choose 2 (which is labelled 4C2 in math-speak - with the 4 a superscript and the 2 a subscript).
In fact, p choose r = #no of ways to choose R objects from a set of P elements = pCr
= p! / (p-r)!r!
where p! = p.(p-1).(p-2)....3.2.1
e.g. 4! = 4.3.2.1 = 12
So for the JJ scenario, p = 4, r = 2
4C2 = 4! / (4-2)!.2! = 12/2x2 = 12/4 = 6
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