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# Solving Result Unknown Problems with Three-digit Numbers.

Lesson 7 of 13

## Objective: SWBAT solve result unknown problems with three-digit numbers.

#### Introduction/Hook

*10 min*

I start class by handing out an entrance ticket. I allow students 5-7 minutes to work on the entrance ticket. This entrance ticket assesses students' understanding of adding four three-digit numbers (a skill that we introduced yesterday). We will use the results of this entrance ticket during the introduction to new material.

**Entrance ticket:**

**The donut shop has 142 chocolate donuts, 320 sprinkle donuts, 115 glazed donuts, and 400 pumpkin donuts. How many donuts does the donut shop have in all?**

When finished with the entrance ticket, have at least one student share his/her response and how he/she solved the problem.

#### Resources

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#### Introduction to New Material

*10 min*

*Now, let’s say that everyone who came to the donut shop bought sprinkle donuts and they sold out. How many donuts does the donut shop have now? *

*Turn and talk: What should I do to solve this problem? *

Students might suggest using the total and subtracting 320 from it. Others might suggest adding up the chocolate, glazed, and pumpkin donuts and leaving the sprinkle donuts out to determine the total. For each strategy suggestion, I have a student model his/her thinking or as the student talks, I model the strategy on the board. Write the students' strategies on the board or on an anchor chart for student reference.

*Now that we’ve talked about strategies for solving a problem like this, please turn your entrance ticket over and solve this problem on the back. *

As students work, circulate to see (1) which strategy they are using and (2) What common mistakes students are making.

After students have finished, have one or two students share their work. Also use this time to correct any potential mistakes or misunderstandings students have.

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#### Guided Practice

*10 min*

*Now I am going to give you a chance to work with a partner and solve a problem similar to the one we worked on as a team. *

When finished, I bring the class back together, and go over the problem, stopping to discuss various strategies and (of course) add them to the strategy chart.

#### Resources

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*Today we have practiced a new skill--solving result unknown word problems with three-digit numbers! We are now going to to show what we know on our Friday Skills Assessment. *

I hand out the Friday Skills Assessment (weekly quiz) and allow students to work independently.

I use data from this assessment to determine which concepts I need to re-teach during my morning math meeting.

#### Resources

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- LESSON 1: What is One Hundred More? What is One Hundred Less?
- LESSON 2: Adding Three-Digit Numbers Without Regrouping
- LESSON 3: Adding Three-Digit Numbers with Regrouping
- LESSON 4: Adding Four Three-Digit Numbers
- LESSON 5: Our Strategies for Result Unknown Problems
- LESSON 6: Two-Step Word Problems (Result Unknown)
- LESSON 7: Solving Result Unknown Problems with Three-digit Numbers.
- LESSON 8: Introduction to Change Unknown Problems
- LESSON 9: How do I solve a change unknown word problem?
- LESSON 10: Acting out Change Unknown Problems
- LESSON 11: Change Unknown Word Problems
- LESSON 12: Change Unknown Word Problems with Number Lines
- LESSON 13: Subtracting Across Zeros