LCM Worksheet
Directions on how to find the LCM (least common multiple) using prime factorization.
1. Write out the numbers
2. On the side create factor trees using the two numbers. Remember to keep going until
you reach a prime number. One is NEVER included in the factor trees.
3. Rewrite the prime numbers from the factor tree next to the original area where you
wrote your numbers.
4. Compare the prime numbers list between each number and circle the pairs in
common.
5. Rewrite the remaining factors. Only include one prime number for every pair.
6. Multiply to find the LCM.
EXERCISES
1. 21, 28 (Find the LCM of the numbers using prime factorization)
2. 56, 64 (Find the LCM of the numbers using prime factorization)
3. You bring water for your soccer team every sixth game. Every third game is a home
game. When will you first bring the drinks to a home game? There are 20 games in a
season. How many times will you bring water to a home game this season?
4. Pencils come in packages of 10. Rulers come in packages of 8. Hannah wants
exactly one pencil for every ruler. What is the smallest number of packages of each
she needs to buy? Explain.