There is an inverse relationship between multiplication and division.

The equation 45 ÷ 5 = 9 has the inverse relationships following are also true:
5 * 9 = 45
9 * 5 = 45

Similar relationships exist for multiplication. The equation 3 * 7 = 21 has the relationships:
21 ÷ 3 = 7
21 ÷ 7 = 3