What are the two smallest common multiples of 4 and 10?

4.

MEDIUM

How many common factors do 20 and 85 have?

5.

MEDIUM

What are the three smallest common multiples of 15 and 18?

6.

MEDIUM

Fanny is buying apples. The number of apples she buys must be both a multiple of 5 and a multiple of 6. Which of the following could be the number of apples she buys?