Ray's New Practical Arithmetic · Examples in Addition and Subtraction · Unit 3: Subtraction

13. Mixed adding and subtracting

Goal: Your child solves problems that need both adding and subtracting, in the right order.

⏱ About 35 minutes · 7 steps

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You'll need

  • The book
  • A slate, small whiteboard or scrap paper
  • A notebook and pencil

What's in the book

Twelve mixed problems, some written across the line with + and − signs and some about a merchant's purchases and payments. Answers are printed.

The lesson, step by step

  1. Warm-up

    Mental: 20 + 15 − 10? 50 − 20 + 5? 100 − 30 − 30?

  2. Reading signs in a row

    Read:

    275 + 381 + 625 − 1098 = ?

    SayAdd all the plus numbers first, then take away. 275 + 381 + 625 = 1281, and 1281 − 1098 = 183.

  3. Several minus signs

    Read:

    6723 − 479 − 347 − 228 = ?

    Show two ways: subtract one at a time, or add 479 + 347 + 228 = 1054 and subtract once. Both give 5669.

  4. Guided practice

    Do problem 3, about the merchant's purchases and payments, together. Make two columns: what came in and what went out.

  5. Independent practice

    Your child does the remaining problems of the set.

  6. Check

    Answers are printed. Compare after each one.

  7. Wrap-up

    Mental story: You have 50 cents, spend 15 and then earn 10. How much now? (45 cents.)

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