Lesson 24 Relate Counting to Addition and Subtraction

    • Let’s subtract by counting on or taking away.

Warm-up Choral Count: Backward from 50

Students thinking

Count backward by 1, starting at 20.

What patterns do you see?

Activity 1 Different Ways to Subtract

Yesterday, we saw Diego’s method to find the value of .

Diego’s way

Ten frame. 7 counters not crossed out. 3 counters crossed out.
Ten frame. 5 red counters crossed out.

Tyler’s way

Ten frame, full. Red, 8. Yellow, 2.
Ten frame. 5 yellow counters.

Find the value of each difference using Diego’s way, then using Tyler’s way.

  1. Diego’s Way

    Tyler’s Way

  2. Diego’s Way

    Tyler’s Way

  3. Diego’s Way

    Tyler’s Way

Activity 2 Find the Number That Makes Each Equation True

Problem 1

Find the number that makes each equation true.
Be sure you can explain your thinking in a way that others will understand.

Set A:

Problem 2

Find the number that makes each equation true.
Be sure you can explain your thinking in a way that others will understand.

Set B:

Practice Problem

Problem 1

Find the value of each difference.
Use the 10-frames if they help.

  1. Double ten frame. 9 counters.

  2. Double ten frame. 10 counters not crossed out. 4 counters crossed out.