Multiplication and Division, Part 2

Lesson 20

Math

Unit 3

3rd Grade

Lesson 20 of 23

Objective


Solve two-step word problems involving all four operations, including multiplying one-digit whole numbers by multiples of 10.

Common Core Standards


Core Standards

  • 3.NBT.A.3 — Multiply one-digit whole numbers by multiples of 10 in the range 10—90 (e.g., 9 × 80, 5 × 60) using strategies based on place value and properties of operations.
  • 3.OA.D.8 — Solve two-step word problems using the four operations. Represent these problems using equations with a letter standing for the unknown quantity. Assess the reasonableness of answers using mental computation and estimation strategies including rounding. This standard is limited to problems posed with whole numbers and having whole-number answers; students should know how to perform operations in the conventional order when there are no parentheses to specify a particular order (Order of Operations).

Foundational Standards

  • 3.NBT.A.2

Criteria for Success


  1. Make sense of a three-act task and persevere in solving it (MP.1).
  2. Solve two-step word problems involving addition, subtraction, multiplication, and division (MP.4), including multiplication of a one-digit number with a multiple of 10 or two-digit number. 
  3. Represent word problems using equation(s) with a letter standing for the unknown quantity (see Tips for Teachers) (MP.2).
  4. Assess the reasonableness of an answer (MP.1).

Tips for Teachers


  • As mentioned in Lesson 11, students will start to write equations to represent select two-step word problems. The Progressions state, "more difficult problems may require two steps of representation and solution rather than one" (OA Progression, p. 28). Thus, it is left to the teacher to decide what "more difficult" means for your students. As some general guidance, it seems reasonable to expect every student to be able to write an equation for all one-step problems and for two-step problems where the unknown is isolated on one side of the equal sign in the equation without needing to manipulate it by the end of the year. For example, see #42 on the New York State Testing Program Grade 3 Common Core Mathematics Test Released Questions May 2016. Since students are expected to do so on the Post-Unit Assessment, this skill is built gradually over the course of Lesson 11, 16, 19, and 20 to prepare students for that.
  • This lesson provides an opportunity to connect two domains in the grade, 3.OA and 3.NBT, when students solve two-step word problems (3.OA.8) involving multiplication of one-digit numbers by multiples of ten (3.NBT.3).
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Anchor Tasks


Problem 1

Act 1: Watch the video Charlie's Gumballs.

a.   What do you notice? What do you wonder?

b.   How many gumballs are there in total? Make an estimate.

Guiding Questions

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References

101Questions Charlie's Gumballs

Charlie's Gumballs by Max Ray is made available on 101Questions under the CC BY 3.0 license. Accessed Nov. 1, 2018, 11:45 a.m..

Modified by Fishtank Learning, Inc.

Problem 2

Act 2: Use the following information to determine how many gumballs there are in total:

  • He split the total gumballs with Jaysen. 
  • After sharing with Jaysen, he split how many he had left with Marinda. 
  • After sharing with Marinda, he split how many he had left with Zack. 
  • Then he gave 5 to his little sister. 
  • He had 10 gumballs left. 

Guiding Questions

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References

101Questions Charlie's Gumballs

Charlie's Gumballs by Max Ray is made available on 101Questions under the CC BY 3.0 license. Accessed Nov. 1, 2018, 11:45 a.m..

Modified by Fishtank Learning, Inc.

Problem 3

Act 3: He started with 120 gumballs. Was your answer reasonable? Why or why not?

Guiding Questions

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References

101Questions Charlie's Gumballs

Charlie's Gumballs by Max Ray is made available on 101Questions under the CC BY 3.0 license. Accessed Nov. 1, 2018, 11:45 a.m..

Modified by Fishtank Learning, Inc.

Problem Set


Answer Keys

Unlock the answer keys for this lesson's problem set and extra practice problems to save time and support student learning.

Discussion of Problem Set

  • In #1, how many more months will Lupe need to save so she has enough to buy the art supplies? How do you know? 
  • What equation did you write for #2? Is there more than one correct equation to represent the situation? How do you know? 
  • Explain the three unknowns you needed to find to solve #3. 
  • How did you solve #5? Which strategy did you use? 
  • Where did you draw your darts in the second part of #6? Is there more than one correct answer? 
  • What made #8 challenging? What did you need to keep in mind in terms of finding the total number of rows on the airplane? 

Target Task


A potter sold 80 vases for $9 each. The potter uses $75 of the money he makes to buy more clay and keeps the rest as spending money. How much spending money does the potter have? 

a.   Write an equation or equations with a letter for the unknown quantity to represent the situation.

b.   Find the solution. Show or explain your work.

Student Response

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Additional Practice


The Extra Practice Problems can be used as additional practice for homework, during an intervention block, etc. Daily Word Problems and Fluency Activities are aligned to the content of the unit but not necessarily to the lesson objective, therefore feel free to use them anytime during your school day.

Extra Practice Problems

Answer Keys

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Word Problems and Fluency Activities

Word Problems and Fluency Activities

Help students strengthen their application and fluency skills with daily word problem practice and content-aligned fluency activities.

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Lesson 19

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Lesson 21

Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Introduction to The Properties of Operations

Topic B: Multiplication and Division by 6 and 7

Topic C: Multiplication and Division by 8 and 9

Topic D: Multiplication and Division by Values Greater than 10

Topic E: Two-Step Word Problems and Patterns in Arithmetic

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