Answer to Question #343927 in Discrete Mathematics for jhon

Question

How many 3-digit numbers can be formed from digits 1 – 5 if:

a. If repetition is allowed?

b. If repetition is not allowed?

Answer 1

a.

$$5^3=125$$

125 3-digit numbers can be formed from digits 1 – 5 if repetition is allowed.

b.

$$P(5,3)=\dfrac{5!}{(5-3)!}=60$$

60 3-digit numbers can be formed from digits 1 – 5 if repetition is not allowed.