What is the mathematical formula for ....

[Ambrose Ackroyd]

My maths is rather rusty.

Could anyone tell me what the mathematical formula is for determining how many unique groups you can make from a finite set of items.

eg. if you have 9 different items, how many unique groups of 3 can you make from that population ?

 

[TheBramble]

Permutations {where ORDER is significant}

M! / (M-S)!

Combinations {where order is not significant - like a lottery}

M! / (M-S)! * S!

M = main set of elements
S = subset of elements

 

[Ambrose Ackroyd]

Many thanks