Also, C(N,R) = N!/{(N-R)!R!} when N! = the product of all numbers from 1 to N.

e.g 4! = 4x3x2x1 = 24

So, C(4,2) = 4!/{(4-2)!2!} = 4!/(2!2!) = 4x3x2x1/(2x1)(2x1) = 24/4 = 6.

If you don't have Excel you can type 4 choose 2 into Google search and it will split out the number [img]/images/graemlins/smile.gif[/img]