Multiplication and Division, Part 1

Lesson 10

Objective

Build fluency with multiplication and division facts using units of 3.

Materials and Resources

Common Core Standards

Core Standards

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  • 3.OA.A.1 — Interpret products of whole numbers, e.g., interpret 5 × 7 as the total number of objects in 5 groups of 7 objects each. For example, describe a context in which a total number of objects can be expressed as 5 × 7.

  • 3.OA.A.2 — Interpret whole-number quotients of whole numbers, e.g., interpret 56 ÷ 8 as the number of objects in each share when 56 objects are partitioned equally into 8 shares, or as a number of shares when 56 objects are partitioned into equal shares of 8 objects each. For example, describe a context in which a number of shares or a number of groups can be expressed as 56 ÷ 8.

  • 3.OA.B.5 — Apply properties of operations as strategies to multiply and divide. Students need not use formal terms for these properties. Example: Knowing that 8 × 5 = 40 and 8 × 2 = 16, one can find 8 × 7 as 8 × (5 + 2) = (8 × 5) + (8 × 2) = 40 + 16 = 56. (Distributive property.) Example: If 6 × 4 = 24 is known, then 4 × 6 = 24 is also known (Commutative property of multiplication.) 3 × 5 × 2 can be found by 3 × 5 = 15, then 15 × 2 = 30, or by 5 × 2 = 10, then 3 × 10 = 30. (Associative property of multiplication.)

  • 3.OA.B.6 — Understand division as an unknown-factor problem. For example, find 32 ÷ 8 by finding the number that makes 32 when multiplied by 8.

  • 3.OA.C.7 — Fluently multiply and divide within 100, using strategies such as the relationship between multiplication and division (e.g., knowing that 8 × 5 = 40, one knows 40 ÷ 5 = 8) or properties of operations. By the end of Grade 3, know from memory all products of two one-digit numbers.

Criteria for Success

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  1. Skip-count by threes. 
  2. Solve multiplication, division, and missing factor problems involving three by skip-counting. (Note: this includes problems where 3 is listed as the first factor, implying the use of the commutative property.)

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  • Problem Set
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Anchor Tasks

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Problem 1

How many?

Guiding Questions

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Problem 2

Solve.

a.    _____ $$= 3\times 8$$

b.    $$30 \div 3 =$$ _____

c.    $$21 =$$ _____ $$\times 3$$

Guiding Questions

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Discussion of Problem Set

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  • How did the skip-counting sequence in #1 help you solve the other problems on the Problem Set?
  • What do you notice about #3c and #3d? What do you wonder? 
  • How did the commutative property help you to solve the equations in #7? 
  • I think the answer in #9c is 18. Do you agree or disagree? What mistake did I make? 
  • Is division commutative? How do you know?

Target Task

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Solve.

1.   $$7\times 3 =$$ ____                 2.   ___ $$= 27\div 3$$                  3.   $$3\times$$ _____ $$=18$$

 

Mastery Response

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