Unit 7 - Lesson 14 - Grade 2: Illustrative Mathematics

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Grade 2 Unit 7
Lesson 14: Think Before You Subtract
CC BY 2021 Illustrative Mathematics®

Instructions

Grade 2 Unit 7
Lesson 14: Think Before You Subtract
CC BY 2021 Illustrative Mathematics®

Lesson: Think Before You Subtract

Which One Doesn’t Belong: Blocks and Blocks and Blocks (Warm Up)

Which one doesn’t belong?

Agree to Disagree

Tyler and Clare are subtracting by place to find the value of 244 - 67. Tyler says he will decompose before
he starts. Clare says she agrees.

The diagrams show each student’s first step.

What is the same about Tyler and Clare’s diagrams? What is different?

Work together to complete Tyler’s way and Clare’s way to find the value of 244 - 67.

What do Tyler and Clare’s diagrams look like after the last step? What is the same about these diagrams? What is different?

Sort and Subtract

Here is a base-ten diagram for 341.

Andre wants to use diagrams and subtract by place to find the value of 341 - 68. He says he will decompose a ten and a hundred to subtract.

Why do you think he said that?

Andre only wants to use a diagram to subtract by place if he will decompose a unit. Help Andre sort the expressions into groups. If you are not sure, use base-ten blocks or a diagram to help.

Find the value of 1 expression from each group.

Show your thinking.

Cool Down: Decompose? Maybe.

Han wants to subtract by place to find the value of these expressions.

Unit 7 - Lesson 14 - Grade 2: Illustrative Mathematics

Which One Doesn’t Belong: Blocks and Blocks and Blocks (Warm Up)

Which one doesn’t belong?

Agree to Disagree

What is the same about Tyler and Clare’s diagrams? What is different?

Work together to complete Tyler’s way and Clare’s way to find the value of 244 - 67.

What do Tyler and Clare’s diagrams look like after the last step? What is the same about these diagrams? What is different?

Sort and Subtract

Andre wants to use diagrams and subtract by place to find the value of 341 - 68. He says he will decompose a ten and a hundred to subtract.

Why do you think he said that?

Andre only wants to use a diagram to subtract by place if he will decompose a unit. Help Andre sort the expressions into groups. If you are not sure, use base-ten blocks or a diagram to help.

Find the value of 1 expression from each group.

Show your thinking.

Han wants to start by subtracting without decomposing any units.

Which expression should he choose?

Find the value of the expression. Show your thinking.

Unit 7 - Lesson 14 - Grade 2: Illustrative Mathematics

Which One Doesn’t Belong: Blocks and Blocks and Blocks (Warm Up)

Which one doesn’t belong?

Agree to Disagree

What is the same about Tyler and Clare’s diagrams? What is different?

Work together to complete Tyler’s way and Clare’s way to find the value of 244 - 67.

What do Tyler and Clare’s diagrams look like after the last step? What is the same about these diagrams? What is different?

Sort and Subtract

Andre wants to use diagrams and subtract by place to find the value of 341 - 68. He says he will decompose a ten and a hundred to subtract. Why do you think he said that?

Andre only wants to use a diagram to subtract by place if he will decompose a unit. Help Andre sort the expressions into groups. If you are not sure, use base-ten blocks or a diagram to help.

Find the value of 1 expression from each group. Show your thinking.

Han wants to start by subtracting without decomposing any units.Which expression should he choose?

Find the value of the expression. Show your thinking.

Andre wants to use diagrams and subtract by place to find the value of 341 - 68. He says he will decompose a ten and a hundred to subtract.

Why do you think he said that?

Find the value of 1 expression from each group.

Show your thinking.

Han wants to start by subtracting without decomposing any units.

Which expression should he choose?