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Parent guide · Grade 2 Math · Unit 5

Lesson 5.2 Subtracting Three-Digit Numbers

Written for the parent. Read the Say this lines aloud as they are, or in your own words. Answers for you are marked Listen for.

At a glance

Time
5 sessions of 20–25 minutes
Goal
Subtract three-digit numbers with the written method.
You need
  • Pencil and crayons
Print
Worksheet A · Worksheet B · the lesson page

Steps

  1. Do this: Ask these out loud. Your child answers out loud; no paper needed.

    • Ask: “What number is ten less than 839?” Listen for: 829
    • Ask: “What number is ten less than 400?” Listen for: 390
    • Ask: “What number is ten more than 405?” Listen for: 415
    • Ask: “What number is ten less than 410?” Listen for: 400
    • Ask: “What number is ten less than 192?” Listen for: 182

  2. Say this: “Start with the ones. Regroup from the tens or hundreds whenever the top digit is too small.”

    Say this: “Check by adding the answer to the number you took away.”

    Say this: “Regroup a hundred: trade 1 hundred for 10 tens.”

  3. Show: 390 − 361 = ___

    Say this: “Ones: 0 is less than 1, so regroup 1 ten as 10 ones. The tens digit becomes 8.”

    Say this: “10 − 1 = 9”

    Say this: “Tens: 8 − 6 = 2”

    Say this: “Hundreds: 3 − 3 = 0”

    Say this: “Check: 29 + 361 = 390”

    Answer: 29

    Show: Gideon had 928 men. He sent 890 home. How many men stayed?

    bar model

    Say this: “Unknown: how many are left.”

    Say this: “Bar model: the whole is 928; one part is 890; the other part is unknown.”

    Say this: “Equation: 928 − 890 = ?”

    Say this: “928 − 890 = 38”

    Say this: “Answer: 38 men stayed.”

    Answer: 38 men. 38 men stayed.

  4. Do this: Your child does these with you. Let them try first; help only after a real try.

    Ask: 462 − 131 = ___

    Listen for: 331

    If stuck: Ones: 2 − 1 = 1

    Ask: 694 − 472 = ___

    Listen for: 222

    If stuck: Ones: 4 − 2 = 2

    Ask: 394 − 193 = ___

    Listen for: 201

    If stuck: Ones: 4 − 3 = 1

    7 more practice items on the lesson page, and on Worksheet A and Worksheet B.

    • Regrouping when it is not needed.

  6. Price a few household items between 100 and 500 cents. Your child adds two prices on paper and checks with a partner. Then find how much more one costs than the other.

  7. Say this: “Tell me what you learned today. Show me with your hands or the counters if you like.”

    Listen for: Subtract three-digit numbers with the written method.

  8. Count by tens and hundreds from any number, forward and back.

Spread over the week

5 sessions of 20–25 minutes. Stop while it is still going well.

  1. Session 1. Warm-up, then teach the new idea (steps 1 and 2).
  2. Session 2. Warm-up again, then show how with the examples.
  3. Session 3. Practice together, then play the game.
  4. Session 4. More practice on the worksheet, and the daily habit.
  5. Session 5. Quick check: narration and a few practice items. Move on when it is mostly right.