Question

Using the prime factor method, find the lowest common multiple of 20 and 12.

Answer 1

60

Explanation:

First, break down each of the numbers into their prime factors.

20 = 2² x 5

12 = 2² x 3

To find the LCM, underline each of the prime numbers. If there is a repeated prime number, underline the one with the largest possible value. For example, if there is 3² and 3³, underline the second one. In this case, the values are the same, so just underline one.

20 = 2² x 5

12 = 2² x 3

Next, multiply all the underlined numbers.

LCM (20, 12) = 2² x 5 x 3 = 60

Answer 2

lcm = 4

Explanation:

20 = 2 × 2 × 5 ← product of prime factors

12 = 2 × 2 × 3 ← product of prime factors

The lowest common multiple (lcm) = 2 × 2 × 5 × 3 = 60