Question

How do we know when to use combinations and when to use permutations?

Answer 1

Permutations are for lists (order matters) and combinations are for groups (order doesn't matter). A joke: A "combination lock" should really be called a "permutation lock". The order you put the numbers in matters. (A true "combination lock" would accept both

Answer 2

The number of possible combination of r objects from a set on n objects. ... Hence , Permutation is used for lists (order matters) and Combination for groups (order doesn't matter) .

For permutation order is very important and for combination it is not as important as it is for permutation.

For permutation we find no. of ways by

n!/(n-p)! r! And for combination we use formula..

n!/(n-c)! r!.

Hope this helps mate !

Thanks :)