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Unit 3 - Lesson 12 - Grade 3: Illustrative Mathematics

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Grade 3 Unit 3
Lesson 12: Subtract Strategically
CC BY 2021 Illustrative Mathematics®
Grade 3 Unit 3
Lesson 12: Subtract Strategically
CC BY 2021 Illustrative Mathematics®
Lesson: Subtract Strategically

Number Talk: Threes (Warm Up)

Find the value of each expression mentally.

2 x 6

3 x 6

2 x 7

3 x 7

How Would You Subtract?

  • Use a strategy or algorithm of your choice to find the value of each difference.
  • Show your reasoning. Organize it so it can be followed by others.

451 - 329

382 - 190

924 - 285

600 - 478

505 - 417

Greatest Difference, Smallest Difference

Directions:
  1. Decide with your partner whether you will try to make the greatest difference or smallest difference.
  2. Take turns spinning and recording a digit in the hundreds, tens, or ones place. Continue until your numbers are complete.
  3. Find the difference.
  4. Compare your values.
  5. Write a comparison using >, <, or =.
  6. Play again.

Round 1

We will make the __________ difference.

Take turns spinning and recording a digit in the hundreds, tens, or ones place. Continue until your numbers are complete.

Find the difference.

Compare your values.
My number __________ my partner's number
Play again.

Round 2

We will make the __________ difference.

Take turns spinning and recording a digit in the hundreds, tens, or ones place. Continue until your numbers are complete.

Find the difference.

Compare your values.
My number __________ my partner's number
Play again.

Round 3

We will make the __________ difference.

Take turns spinning and recording a digit in the hundreds, tens, or ones place. Continue until your numbers are complete.

Find the difference.

Compare your values.
My number __________ my partner's number
Play again.

Round 4

We will make the __________ difference.

Take turns spinning and recording a digit in the hundreds, tens, or ones place. Continue until your numbers are complete.

Find the difference.

Compare your values.
My number __________ my partner's number
Play again.
Cool Down: An Algorithm or Another Strategy?

How would you find the value of 700 - 599? Explain your reasoning.