Multiplication and Division of Whole Numbers

Lesson 7

Objective

Multiply three-digit numbers by two-digit numbers.

Materials and Resources

Common Core Standards

Core Standards

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  • 5.NBT.B.5 — Fluently multiply multi-digit whole numbers using the standard algorithm.

Foundational Standards

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  • 4.NBT.B.4

  • 4.NBT.B.5

  • 5.NBT.A.1

  • 5.NBT.A.2

Criteria for Success

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  1. Compute two-digit by three-digit products using the standard algorithm, the partial products algorithm, or the area model. 
  2. Understand that the most efficient way to solve a multiplication problem with the standard algorithm is by decomposing the value with the fewest number of non-zero digits (i.e., by having the value with fewer non-zero digits on the bottom since it will produce the fewest number of partial products). (Note: This criteria for success can be delayed until a later lesson.) 
  3. Assess the reasonableness of an answer by rounding to estimate two-digit by three-digit products (MP.1).
  4. Solve word problems involving up to three-digit by two-digit multiplication (MP.4).

Tips for Teachers

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Throughout the remainder of the unit, the focus will be on the standard algorithm instead of the partial products algorithm or the area model. However, you may decide to include those models in your discussions, depending on student need. 

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Anchor Tasks

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Problem 1

Find the products using any method. Then assess the reasonableness of your answer.

  1.   814 x 39
  2.   715 x 53
  3.   78 x 266

Guiding Questions

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Problem 2

How many cans of soda are in the following display? There are 12 cans of soda in each box.

Guiding Questions

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References

The Mind of an April Fool American Pepsi

American Pepsi is made available on The Mind of an April Fool under the CC BY-NC 4.0 license. Accessed Dec. 7, 2018, 12:38 p.m..

Modified by The Match Foundation, Inc.

Discussion of Problem Set

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  • How many colored pencils are in the supply closet in #2? Did anyone use an area model to solve? Why can we use an area model to solve even though it’s not an area problem? 
  • How much will Jack save in #3? What made this word problem more difficult than the one in #2? 
  • Look at #4. Did anyone see that their answer was unreasonable after they estimated the product?

Target Task

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Problem 1

783 x 42

References

EngageNY Mathematics Grade 5 Mathematics > Module 2 > Topic B > Lesson 6Exit Ticket, Question b

Grade 5 Mathematics > Module 2 > Topic B > Lesson 6 of the New York State Common Core Mathematics Curriculum from EngageNY and Great Minds. © 2015 Great Minds. Licensed by EngageNY of the New York State Education Department under the CC BY-NC-SA 3.0 US license. Accessed Dec. 2, 2016, 5:15 p.m..

Modified by The Match Foundation, Inc.

Problem 2

There are 36 boxes of colored pencils in a supply closet. Each box has 144 pencils in it. What is the total number of colored pencils in the supply closet?

References

Massachusetts Department of Elementary and Secondary Education Spring 2018 Grade 5 Mathematics TestQuestion Stem #20

Spring 2018 Grade 5 Mathematics Test is made available by the Massachusetts Department of Elementary and Secondary Education. © 2017 Commonwealth of Massachusetts. Accessed Dec. 4, 2018, 2:38 p.m..

Mastery Response

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