# GCF and LCM Word Problems

Lesson 8 of 16

## Objective: SWBAT: • Define LCM, and GCF • Solve word problems involving LCM and GCF.

## Big Idea: When would you come across GCF and LCM? Students apply their knowledge of GCF and LCM to solve word problems.

*60 minutes*

#### Do Now

*10 min*

See my **Do Now** in my Strategy folder that explains my beginning of class routines.

Often, I create do nows that have problems that connect to the task that students will be working on that day. Here, students are reviewing factors, multiples, GCF, and LCM. A common mistake is students confuse GCF and LCM. I quickly go over correct answers with students.

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#### Problems

*15 min*

I have students work in partners on these two problems. I don’t mention anything about LCM and GCF. If students struggle, that’s okay. I encourage them to use what they know to do *something. *Students will use different strategies to solve these problems, and that’s great!

After about 10 minutes I have students go to the next page. Students participate in a Think Write Pair Share.

I want students to notice that problem 1 is asking for the *smallest* number of buns and hot dogs you need to buy if you want the *same* number of each. Some students will connect this to finding the LCM of 8 and 10. I want student to notice that problem 2 is *splitting *pearls and beads up into *equal *groups. The question is asking for the *largest *number of identical necklaces. Some students will connect this to GCF.

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#### More Problems

*25 min*

I use the ticket to go data from the previous lesson **(Multiples, LCM, and GCF) **to create homogeneous groups for this part of the lesson. This way students can work with other students who are around their same skill level. I go over group expectations and pass out the Group Work Rubric. I have printed one set of GCF and LCM problem cards for each group. I cut them out and put them in an envelope. I explain that students will receive an envelope with the problems they will work on. See my **Creating Homogeneous Groups** and **Using the Group Work Rubric **videos in my Strategy Folder for more details.

As students are working I walk around to fill out rubrics and monitor student progress. I am looking to see what strategies students are using and how they are showing their work. Students are engaging with **MP 1: Make sense of problems and persevere in solving them. **

If students struggle I may intervene in one of these ways:

- What is the problem asking?
- What do you know from the problem?
- What do you see going on in your head when you read this problem?
- How could you show what is going on in the problem?
- Look back at problem A and B. Is this problem similar to either of those problems? Why or why not?
- Offer the student(s) a multiplication chart or Factor reference sheet

I **Post A Key** around the room, so groups can check their answers as the complete them. If a group successfully completes the problems, they can work on the challenge problems.

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##### Similar Lessons

Environment: Urban

Environment: Urban

Environment: Urban

- UNIT 1: Intro to 6th Grade Math & Number Characteristics
- UNIT 2: The College Project - Working with Decimals
- UNIT 3: Integers and Rational Numbers
- UNIT 4: Fraction Operations
- UNIT 5: Proportional Reasoning: Ratios and Rates
- UNIT 6: Expressions, Equations, & Inequalities
- UNIT 7: Geometry
- UNIT 8: Geometry
- UNIT 9: Statistics
- UNIT 10: Review Unit

- LESSON 1: Welcome to 6th Grade Math
- LESSON 2: R-E-S-P-E-C-T
- LESSON 3: Tiles and Toothpicks
- LESSON 4: Mindset
- LESSON 5: Pretest
- LESSON 6: Brownies & Factors
- LESSON 7: Multiples, LCM, and GCF
- LESSON 8: GCF and LCM Word Problems
- LESSON 9: Show What You Know: Factors and Multiples + Introduction to Exponents
- LESSON 10: Why do we need an Order of Operations?
- LESSON 11: Order of Operations
- LESSON 12: True/False Equations: Working with the Order of Operations + Show what you know
- LESSON 13: Equivalent Numerical Expressions, Day 1 of 2
- LESSON 14: Equivalent Numerical Expressions, Day 2 of 2
- LESSON 15: Unit Review
- LESSON 16: Unit Test