What is the lowest common multiple (LCM) of 4 and 5?

To determine the lowest common multiple (LCM) of two numbers, we are looking for the smallest positive integer that is a multiple of both numbers. For the numbers 4 and 5, the multiples can be listed as follows:

• The multiples of 4 are: 4, 8, 12, 16, 20, 24, 28, 32, 36, etc.

• The multiples of 5 are: 5, 10, 15, 20, 25, 30, 35, 40, etc.

Next, we find the smallest number that appears in both lists. Both lists contain the number 20 as a multiple. Therefore, the LCM of 4 and 5 is 20.

In mathematical terms, the LCM can also be calculated by using the formula:

[ \text{LCM}(a, b) = \frac{|a \times b|}{\text{GCD}(a, b)} ]

For 4 and 5, the greatest common divisor (GCD) is 1 (since they have no common factors other than 1), thus:

[ \text{LCM}(4, 5