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Welcome to the guide on LCM and GCF

Please note this topic is a big differentiator in getting a high score

There are no Prerequisites for this lesson. 

First, let's get a better understanding of what LCM (Least Common Multiple) and GCF (Greatest Common Factor) are, by visiting the links below:

Once you get a better understanding of what to do when solving a LCM and GCF problem, try out some of the practice websites below. If you need help on how to solve a problem, try reviewing the links above!

  • Basic Drill (A PDF question bank with answers at the end) 

  • More Practice (A classic site to review. Do as many questions as you would like to make you feel comfortable) 

  • Questions and detailed explanations (An interactive site with questions, answers, and explanations to guide your learning)

Finally, try out some of our own practice problems to make sure you really understand the content!

1. Tyrone is looking for his favorite granola bars while he is out at his local convenience store. He wants to buy enough to last him a while without having to buy them again, so he looks for his usual hunk of chunk chocolate chip and s’more flavored granola bars. Unfortunately, he can't find any other than 5 bar packs of hunk of chunk chocolate flavor and a 6 bar packs of s’more flavor. He wants to have the same amount of each, how many packs should he buy in total?

2. Darnell has a large bag of skittles and m&ms for Halloween. He wants to divide the skittles and m&ms into equal groups, of the largest size possible, to put into bags that he will give out to trick or treaters. Darnell counts out the skittles and m&ms and gets a total of 285 for the skittles and 330 for the m&ms. How many skittles and m&ms were in each bag given out?

3. Giorno is a scientist, he is currently running a test on a specific strain of bacteria. The bacteria has a population size of 500. He has another strain of bacteria, that has a population of 575. He wants to divide the bacteria of each strain into equal groups. Wasting as little as possible, What is the greatest possible size of each group?

4. Mark and Ralph have a collection of marbles. Mark has 20 marbles, and Ralph has 15 marbles. If Ralph and Mark were able to add to their marble collection the amount of marbles they currently have, what is the least number of times Ralph will have to add to his collection to equal Mark’s marbles? (To clarify Ralph will add 15 marbles to his collection each time).

5. Robbie, an aspiring tennis player, made a goal to practice a lot more during the offseason so he would be better prepared for when the Spring season started. He needed a lot more tennis balls, so he looked up on amazon for different balls. He found two different highly rated ball companies that sold balls in packages of 8 and 9 for a good price. He wanted as many balls as he could get, so he decided, perhaps unwisely, to buy the same amount of both. What is the least number of balls he could have bought to have an equal number of balls from both companies?

6. Find the GCF of the following numbers: 48, 96, 120:

7. Find the LCM of the following numbers: 11, 12, 6:

8. Franky is given the important task of getting some of the snacks for a party in a large company. He wants to add donuts to the available snacks, but is torn between two different flavors, jelly filled and original glazed. In the end, he decides to buy an equal amount of both. Unfortunately, the jelly filled only came in boxes of 10 donuts and the glazed donuts were only available in boxes of 8. How many boxes of jelly filled will Franky need to have the same amount of glazed and jelly filled donuts?


Click here to view the answers.

Congrats on reaching the end of this lesson. If you did not understand any concept be sure to go back through and review, so that you can be fully prepared. We learn the most from our mistakes so don’t be disheartened by them. When you feel that you are ready, go ahead and take a little break. Then come back and move onto another section!

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