Question

Ruth has the following set of refrigerator magnets: {A, B, C, D, E}. (a) How many different three-letter strings can she form with these magnets? (b) How many different three-letter strings can she form if the middle letter must be a vowel?

Answer 1

a. 60

b.24

Explanation:

a. We use permutation, it would be 3 taken out of 5, or 5*4*3

b.if A or E must be used, then we have 4*3*2