Lesson 15 Decompose a Ten and a Hundred to Subtract

    • Let’s subtract within 1,000.

Warm-up Choral Count: Hundreds and Tens

Count back by 10, starting at 590.

What patterns do you see?

Activity 1 Elena’s Thinking

Elena’s thinking:

Step 1:

Subtraction. 7 hundreds, 2 tens, 6 ones minus 5 hundreds, 5 tens, 8 ones. 

Step 2:

Subtraction. 7 hundreds, 2 tens, 6 ones minus 5 hundreds, 5 tens, 8 ones. Decomposing 2 tens and 6 ones to 1 ten and 16 ones.

Step 3:

Subtraction. 7 hundreds, 2 tens, 6 ones, decomposed into 6 hundreds, 11 tens, 16 ones minus 5 hundreds, 5 tens, 8 ones.  

  1. Use base-ten blocks or a base-ten diagram to show Elena’s steps.

  2. Finish Elena’s work to find the value of .

  3. What is another way you could use numbers or equations to show subtracting by place to find the value of ?

Activity 2 Walk About and Subtract

Students playing card game with base ten blocks.

  • Find someone with a different number than you.

  • Find the difference between your numbers.

    • Show your thinking.

  • Trade cards and find a new partner.

  1. Partner 1:

  2. Partner 2:

  3. Partner 3:

Practice Problem

Problem 1

Find the value of each difference. Show your thinking.