Curriculum  /  Math  /  4th Grade  /  Unit 2: Multi-Digit Multiplication  /  Lesson 11

Multi-Digit Multiplication

Lesson 11

Math

Unit 2

4th Grade

Lesson 11 of 18

Objective

Multiply two-digit multiples of 10 by two-digit multiples of 10. Estimate multi-digit products by rounding numbers to their largest place value.

Common Core Standards

Core Standards

  • 4.NBT.B.5 — Multiply a whole number of up to four digits by a one-digit whole number, and multiply two two-digit numbers, using strategies based on place value and the properties of operations. Illustrate and explain the calculation by using equations, rectangular arrays, and/or area models.

Foundational Standards

  • 3.NBT.A.3
  • 4.NBT.A.1
  • 3.OA.C.7

Criteria for Success

  1. Multiply multiples of 10 by multiples of 10.
  2. Identify patterns in multiplication of multiples of 10 by multiples of 10 (MP.8). 
  3. Estimate products of two-digit by two-digit multiplication by rounding the multi-digit values to their largest place value.

Tips for Teachers

  • Throughout this topic and then next one, “when students decompose numbers into sums of multiples of base-ten units to multiply them, they are seeing and making use of structure (MP.7). As they illustrate and explain the calculation by using physical or drawn models, they are using appropriate drawn tools strategically (MP.5) and attending to precision (MP.6) as they use base-ten units in the appropriate places” (PARCC Model Content Frameworks, Mathematics, Grades 3–11).
  • It is important to preserve place value when talking about products of multi-digit numbers. For example, when discussing the computation $$68 \times 74$$, the partial product of the 6 digit and the 4 digit should be referenced as “six tens times four” or “sixty times four” rather than “six times four.”
  • In Lessons 11—15, students estimate products of two two-digit whole numbers by rounding both factors to their largest place, thus connecting the work of 4.NBT.3 across clusters to the work of 4.NBT.4, as well as preparing students to assess reasonableness in the context of multi-step word problems (4.OA.3).

Lesson Materials

  • Optional: Base ten blocks (18 ones, 18 tens, 18 hundreds, and 18 thousands per student or small group) — Students might not need these depending on their reliance on concrete materials.
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Anchor Tasks

25-30 minutes

Problem 1

a.   Solve. 

  1. 6 × 3 = _____
  2. 60 × 3 = _____
  3. 60 × 30 = _____

b.   What do you notice about Part (a)? What do you wonder?

Guiding Questions

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Student Response

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Problem 2

a.   Kristen and Rajiv are finding the product 80 × 50. Kristen says to find 8 × 50, then multiply by 10. Rajiv says to find 80 × 5, then multiply by 10. 

  1. Will both Kristen and Rajiv’s methods give the correct product? Why? 
  2. Write expressions to represent Kristen and Rajiv’s methods. 

b.   Find the product 80 × 50. 

Guiding Questions

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Student Response

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Problem 3

Estimate the following products. 

a.   41 × 32

b.   57 × 45

c.   24 × 77

Guiding Questions

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Student Response

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Problem Set

15-20 minutes

Discussion of Problem Set

  • What pattern did you notice while solving #1?
  • What made #2(d) and #2(h) particularly more challenging? 
  • Think about the problems we solved during the lesson and the problems you solved in the Problem Set. When does the number of zeros in the factors not equal the number of zeros in the product?
  • For each problem in #4, would you expect the actual product to be greater or less than your estimate? Why? 
  • How can you tell, just by looking at the size of the factors and the size of the product Josh found, that his answer is unreasonable? 

Target Task

5-10 minutes

Problem 1

Find the following products.

a.   20 × 40

b.   60 × 70

c.   20 × 50

Student Response

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Problem 2

Estimate the following products.

a.   32 × 81

b.   48 × 59

c.   25 × 73

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.

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.

Next

Multiply two-digit multiples of 10 by two-digit numbers.

Lesson 12
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Lesson Map

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

Topic A: Multiplicative Comparison

Topic B: Multiplication of up to Four-Digit Whole Numbers by One-Digit Whole Numbers

Topic C: Multiplication of Two-Digit Whole Numbers by Two-Digit Whole Numbers

Topic D: Multi-Step Word Problems

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