Question

nPr and nCr; what are they? How are they used in probability?

An explanation of why they work would be good too,

A link to somewhere for me to read for myself would be fine.

Answer 1

nPr is the notation for permutations.
nCr is the notation for combinations.
They are very important in probability, because they determine the number of possibilities to arrange a set of items.

http://www.mathsisfun.com/combinatorics/combinations-permutations.html

Answer 2

Thanks.