What is the least common multiple of 4 and 5?

To determine the least common multiple (LCM) of 4 and 5, we first identify the multiples of each number:

• The multiples of 4 are: 4, 8, 12, 16, 20, ...

• The multiples of 5 are: 5, 10, 15, 20, 25, ...

The LCM is the smallest multiple that both numbers share. By looking through the two lists of multiples, we can see that the number 20 is the first multiple that appears in both lists.

Furthermore, 20 can be derived by multiplying the two numbers together (4 × 5 = 20), which is one way to calculate the LCM of two numbers that are relatively prime, like 4 and 5. Since they share no common factors besides 1, the product gives the LCM directly.

So, the least common multiple of 4 and 5 is indeed 20.