Im glad you got it.Permutations are where the order DOES matter.Combinations are where the order does NOT matter. c00ky83 tells you above how to go from permutations to combinations. You divide by the factorial of the number of items in the set - in this case 5!
There are y ways of selecting the first number leaving y-1 objects There are y-1 ways of selecting the second number leaving y-2 objects There are y-2 ways of selecting the third number leaving y-3 objects and so on until . . . There are y-(N-1) ways of selecting the Nth number leaving y-N objects
The total number of permutations is found by multiplying these together
= y * (y-1) * (y-2) * . . . . * (y-(y-1))
This can also be written as y! / (y-N)! (the ! means factorial)
Thanks again gen. I've done a few examples and got it for sure now. I have an HNC (from Roman times) in Telecomms engineering but haven't done any maths for ages. This site with people like you will be a great help in keeping the old brain alive.