What is the least common multiple of 4 and 5?

To find the least common multiple (LCM) of 4 and 5, we need to identify the smallest multiple that both numbers share.

First, we can list the multiples of each number:

• The multiples of 4 are: 4, 8, 12, 16, 20, 24, ...

• The multiples of 5 are: 5, 10, 15, 20, 25, 30, ...

Next, we look for the smallest number that appears in both lists.

From the lists above, the first common multiple is 20. This shows that 20 is a multiple of both 4 (since (4 \times 5 = 20)) and 5 (since (5 \times 4 = 20)).

Therefore, the least common multiple of 4 and 5 is 20, confirming that the correct answer is indeed the option that specifies 20 as the least common multiple. This concept is foundational in understanding how to find common multiples, which is essential in various math applications, including adding and subtracting fractions and solving problems involving ratios.