Question

You want to make five-letter codes that use the letters A, F, E, R, and M without repeating any letter. What is the probability that a randomly chosen code starts
with A?


A-0.10

B-0.15

C-0.20

D-0.25

Answer 1

There are 5 letters to choose from. So you have 5*4*3*2*1 = 120 different ways to arrange them (order matters and no repeats are allowed)

Answer 2

Now if you make A the first letter, then you have 4 letters to arrange in the 4 remaining slots. So you have 4*3*2*1 = 24 ways to do that.

Answer 3

Divide the two to get the probability: 24/120 = 1/5 = 0.20