Order

is important

Order is NOT important

 

Arrange

Permutations

Arrange and Pick

Variations

Pick

Combinations

 

Without

repetition




Example

How many ways are there to arrange 3 letters a,b,c?

 

 

How many words of 2 different letters can you make with 4 letters a,b,c,d?

How many ways are there to pick 2 different letters out of 4 letters a,b,c,d? [number of subsets]

 

With

repetition

 

 

 

 

 

 
Example

How many ways are there to arrange 2 letters a and 2 letters b?

 

How many words of 2 letters can you make with 4 letters a,b,c,d?

How many ways are there to pick 2 letters out of 4 letters a,b,c,d?

Dirk Van de moortel 2003