LCM Problem: Finding the Least Common Multiple of 5 and 9

To find the least common multiple (LCM) of 5 and 9, list the multiples of each number and find the smallest multiple they have in common.

Multiples of 5: $5, 10, 15, 20, 25, 30, 35, 40, 45, \ldots$

Multiples of 9: $9, 18, 27, 36, 45, \ldots$

The smallest common multiple is $45$.