Difference between Permutations and Combinations

 Often students confuse between Permutations and Combinations. While both are used to find ways to do a specific job, in permutation order is important whereas in combinations, order is not important

Lets take a simple example 

Question - How many 4 color stripes flags can be made using six different colors. Repetition is not allowed.

There is a proper order and there are restrictions so we will use permutation.

nPr = n!/(n-r)! = 6!/(6-4)! = 6!/2! = 6*5*4**3 = 360

Question - How many 4 color stripes flags can be made using six different colors. Repetition is allowed.

As repetition is allowed and there is no proper and restrictions, we can use combinations here

nCr = n!/r(n-r)! = 6!/

If the order doesn't matter, it is a Combination. If the order does matter it is a Permutation.

I have made a detailed video on this topic, will upload soon on YouTube.

You can practice this chapter on Testpanda.com