Right and Wrong Permutations and Combinations Methods And Pointers That Will Make You Ace These On Your CSET Exam

n = 3 because there are three letters in this problem. r = 3 because we are arranging all three letters at once.

We now plug n and r into our permutation formula:

We can visualize this by writing out the permutations and checking it against our answer:

1 = ABC
2 = ACB
3 = BAC
4 = BCA
5 = CAB
6 = CBA

Example: Out of a pool of 10 candidates, how many ways can voters select a president, vice president and treasury, assuming that the same person cannot hold more than one office.

n = 10 because there are 10 candidates to choose from in this problem. r = 3 because there are three offices and so we are looking at 3 people at a time.

We now plug n and r into our permutation formula:

The only other permutation formula you may need to know for the CSET is when some of the items are identical.

Example: How many permutations are there for the letters in the word, HAPPY?