Multiplication and Division, Part 2

Lesson 2

Math

Unit 3

3rd Grade

Lesson 2 of 23

Objective


Understand the zero and identity properties of multiplication.

Common Core Standards


Core Standards

  • 3.OA.A.4 — Determine the unknown whole number in a multiplication or division equation relating three whole numbers. Determine the unknown whole number in a multiplication or division equation relating three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 × ? = 48, 5 = _ ÷ 3, 6 × 6 = ?
  • 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.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.
  • 3.OA.D.9 — Identify arithmetic patterns (including patterns in the addition table or multiplication table), and explain them using properties of operations. For example, observe that 4 times a number is always even, and explain why 4 times a number can be decomposed into two equal addends.

Foundational Standards

  • 3.OA.A.1
  • 3.OA.A.2
  • 3.OA.B.6

Criteria for Success


  1. Look for and express regularity in repeated reasoning when multiplying by $$1$$ to generalize the pattern of multiplying any number by $$1$$ results in a product that is just that number (i.e., $$1\times n = n$$) (MP.8).
  2. Look for and express regularity in repeated reasoning when multiplying by $$0$$ to generalize the pattern of multiplying any number by $$0$$ results in a product that is $$0$$ (i.e., $$0\times n=0$$) (MP.8).
  3. Use the two properties mentioned above as well as the relationship between multiplication and division to determine the unknown whole number in a multiplication or division equation relating three whole numbers, one of which is $$0$$ or $$1$$
  4. Explain why any number divided by $$0$$ results in an impossible product by rewriting the division sentence as a multiplication one to see that no such value exists (e.g., $$6 \div 0 = a \rightarrow a\times 0 = 6$$, and no such a exists since any number multiplied by $$0$$ would have a product of $$0$$) (MP.3). 

Tips for Teachers


Students are not expected to use the terms "zero property" or "identity property," but they are included in the objective so that teachers can understand this lesson’s connection to the topic. Teachers may choose to rewrite the objective to be more student-friendly if they use objectives in a student-facing way.

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Anchor Tasks


Problem 1

Rudy is waiting patiently for his new hens to lay some eggs.

a.   On Monday he went to the henhouse to check their nests. He has 12 hens in the house, and each hen had laid 0 eggs. How many eggs did Rudy have in total? Write an equation to represent the situation.

b.   On Tuesday when he went to the henhouse, he discovered that each of his 12 hens had laid 1 egg! How many eggs does he have now? Write an equation to represent the situation.

Guiding Questions

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References

Achievement First Grade 3, Unit 1, Lesson 16 (2018-2019)Pose the Problem

Grade 3, Unit 1, Lesson 16 (2018-2019) is made available by Achievement First as a part of their Open Source web portal under a CC BY 4.0 license. Copyright © 1999-2017 Achievement First. Accessed Nov. 9, 2018, 3:07 p.m..

Modified by Fishtank Learning, Inc.

Problem 2

Solve.

a.   $$4\times 1 = $$ _____

b.   _____ $$= 1\times 7$$

c.   $$5\ \times$$ _____ $$=5$$

d.   $$6\div 6 = $$ _____

e.   _____ $$=9\div1$$

Guiding Questions

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Problem 3

Solve. 

a.   $$2\times 0 = a$$

b.   $$b = 0\times 3$$

c.   $$7\times c = 0$$

d.   $$0\div 8 = d$$

Guiding Questions

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Problem Set


Answer Keys

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Discussion of Problem Set

  • Discuss with a partner what patterns for multiplying and dividing by $$0$$ and $$1$$ helped you solve #1? #5? 
  • What pattern for multiplying by $$1$$ does #3 represent?
  • Why was A incorrect in #4? What would the correct quotient be? 
  • Why were you able to compare $$0\div43$$ with $$96\times 0 $$ even though we don’t know how to compute with numbers as large as $$43$$ and $$96$$? 
  • Which problems show that we can’t define a single specific value when we divide by $$0$$? 
  • How is multiplying by $$1$$ and multiplying units of $$1$$ similar to adding $$0$$ to a number?
  • Let’s fill out more of the multiplication table based on what we’ve learned today. Why do you think there are no squares that correspond with the $$0$$ facts? 

Target Task


Determine the value of the unknown number that makes each equation below true.

a.   $$6=a \times 1$$

b.   $$8 \times b = 8$$

c.   $$0=c \div 5$$

d.   $$6 \times d = 0$$

e.   $$1 =7 \div e$$

f.   $$1\times f=9$$

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

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Lesson 1

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Lesson 3

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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