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Multiply Numbers Larger Than 20

Grade 3: Unit 4: Lesson 16

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Let’s multiply numbers that are larger than 20.

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Number Talk: Three Times Some Numbers

Warm-Up

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Find the value of each expression mentally.

3 x 10

3 x 20

3 x 50

3 x 25

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Let’s Talk About It!

How did the first three problems help you solve the last problem?

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4 x 23, Represented

Activity 1

MLR 8: Discussion Supports

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Here is how Clare and Andre represented 4 x 23.

a. How does each diagram show 4 x 23 ?

b. How could we use Clare’s diagram to find the value of 4 x 23 ?

c. How could we use Andre’s diagram to find the value of 4 x 23 ?

Launch

• Groups of 2

• “Take a minute to make sense of how Clare and Andre represented .”

• 1 minute: quiet think time

• Give students access to grid paper and base-ten blocks.

Student Work Time

• “Now, work with your partner to complete the first two problems about .”

• 8–10 minutes: partner work time

• Monitor for the diagrams that students choose in Diego’s problem and for their explanations.

• Pause for a discussion. Invite students to share their responses.

• If not mentioned by students, clarify that all diagrams can be used to multiply 4 and 23, but not

all are equally practical.

• Select a student to explain why diagram D might be more productive than the other diagrams.

• “Now, work independently to complete the last problem.”

• 2–3 minutes: independent work time

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Diego tried different ways to partition or split a diagram to help him find the value of 4 x 23.

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Find the value of 4 x 23.

Show your thinking using diagrams, symbols, or other representations.

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Let’s Talk About It!

What representations did you use in the last question to show ?

How did they help you find the product?

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Some Find Products

Activity 2

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To find the value of 2 x 37, Mai started by writing this equation:

2 x 30 = 60

Describe or show what Mai would do to finish finding the value of 2 x 37.

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Find the value of each product. Show your reasoning.

3 x 32�
2 x 43�
4 x 22�
3 x 29

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Let’s Talk About It!

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Play Close to 100, Multiplication

Activity 3

Engagement

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Play Close to 100, Multiplication with a partner.

1. Place the cards face down.�

2. Each player draws 4 cards.�

3. Each player chooses 2 cards to complete the expression to make a value as close to 100 as possible. Write the 2 digits and the product.�

4. Player closest to 100 wins.�

5. Play 5 rounds. Player who wins the most rounds wins.

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Lesson Synthesis

In the past few lessons, we saw and used different strategies to multiply larger numbers
What were some of those strategies?
What strategies for multiplying do you prefer for finding the value of a product such as ?

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Multiply Numbers Greater Than 20

Cool-Down

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What’s the value of 4 x 24 ? Explain or show your reasoning.

Cool-Down: Multiply Numbers Greater Than 20

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