what is npr and ncr?

P stands for permutations and C stands for combinations.

Here is a introductory video clip on combinations and permutation.

https://www.youtube.com/watch?v=hJRXKq2GEo8

3C2 means how many combinations of 2  can you get from 3 objects   I'll call them  A,B,C

Well you can get  AB, AC, or BC  so    3C2=3

3P2 means how many permutations of 2  can you get from the 3 objects 

Well with permutations order counts so you can have

AB or BA, AC or CA, BC or CB      SO     3P2=6

nCr means how many combinations of r objects can you take from n objects.

nPr means how many permutations of r objects can you take from n objects.     

NPR stands for National Public Radio and NCR is a computer company.

Good one JJ.

We have a new troll in the making.