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Parent guide · Grade 2 Math · Unit 1

Lesson 1.2 Subtraction Strategy Review

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 by thinking addition and by going back through ten.
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: “4 + 8” Listen for: 12
    • Ask: “7 + 7” Listen for: 14
    • Ask: “4 + 9” Listen for: 13
    • Ask: “3 + 8” Listen for: 11
    • Ask: “5 + 3” Listen for: 8

  2. Say this: “For 15 − 8, think 8 + 7 = 15, so 15 − 8 = 7.”

    Say this: “Or go back through ten: 15 − 5 = 10, then 10 − 3 = 7.”

    Say this: “Difference: the answer to a subtraction.”

  3. Show: 14 − 7 = ___

    Say this: “Take away to get to ten: 14 − 4 = 10”

    Say this: “Take away the rest: 10 − 3 = 7”

    Answer: 7

    Show: The orchard had 14 apples on a tree. The children picked 10. How many apples are left on the tree?

    bar model

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

    Say this: “Bar model: the whole is 14; one part is 10; the other part is unknown.”

    Say this: “Equation: 14 − 10 = ?”

    Say this: “14 − 10 = 4”

    Say this: “Answer: 4 apples are left.”

    Answer: 4 apples. 4 apples are left.

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

    Ask: 12 − 4 = ___

    Listen for: 8

    If stuck: Take away to get to ten: 12 − 2 = 10

    Ask: 13 − 4 = ___

    Listen for: 9

    If stuck: Take away to get to ten: 13 − 3 = 10

    Ask: 9 − 9 = ___

    Listen for: 0

    If stuck: 9 − 9 = 0

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

    • Subtracting the smaller digit from the larger: 15 − 8 is not 13.

  6. Fill a 4 × 4 grid with numbers 2–18. Call out facts like “8 + 7” or “15 − 9.” Cover the answer. Four in a row wins.

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

    Listen for: Subtract by thinking addition and by going back through ten.

  8. One-minute fact drill on Fridays (aim for 30 correct). Count by twos to 50 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.