Permutation and combination

Question

Can anybody tell me how to determine whether a particular sum relates to permuatat or combinat?what is the major difference and what are the clues that indicates that a sum requires permutation formula or combinationa formula. 

Answer 1

In English a combination lock is one in which the order of the numbers makes a difference:

123, is different from 321.

Yet in mathematics in a combination order does not make a difference:

ABC is the same as CBA.

 

In mathematics if order makes a difference, if ABC is different from CBA, it is called a permutation.

 

Answer 2

Permutations are used when order matters, and if order doesn't matter then use combinatioN. 

 

An example of these differences is how many ways can we choose 4 people out of 10 for the executive committee (combination of 4 from 10) vs how many ways can we choose 4 people from 10 people to the offices of president, vp, secretary and treasurer (permutatio of 4 from 10)