How do you find the LCM of 6 and 15?

Answer 1

The same as you find the lcm of any other numbers.

1) For small numbers, you can just try out multiples of the larger number (in this case, 15). Is 15x1 a multiple of 6? Is 15x2 a multiple of 6? Continue until you find one.

2) You might also split each number into prime factors, and include - for the result - all the factors that appear in at least one of the numbers.

3) For large numbers, both of these methods are impractical (way too slow). Specifically, there is no efficient method known for factoring large numbers. In this case, use Euclid's Algorithm to calculate the greatest common factor. Then, use the rule that the product of the two numbers is equal to the LCM x the GCF of the two numbers.

Answer 2

2 x 3 = 6

3 x 5 = 15

2 x 3 x 5 = 30, the LCM