Ray's New Primary Arithmetic · Lesson XXXIV · Unit 4: Subtraction

34. Subtracting 10

Goal: Your child knows by heart every fact that takes 10 from a number up to 20, and uses them in story problems.

⏱ About 15 minutes · 7 steps

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You'll need

  • About 20 small counters: dried beans, buttons, pennies or pebbles (the book suggests marbles, beans or pebbles)
  • A slate, small whiteboard or paper and pencil

What's in the book

The table of facts that take 10 away, up to "10 from 20 leaves 10", then story problems. The first has a worked solution.

The lesson, step by step

  1. Warm up

    Five quick facts from the earlier subtraction tables (or, for this first one, from the addition tables).

  2. Build it with counters

    Put out 11 beans and take 10 away. How many are left? Then start with 12 and take 10 away, and so on.

    Say each fact in full: "10 from 12 leaves 2."

  3. Link to adding

    Show that 10 and 3 are 13, so 10 from 13 leaves 3. Every subtraction fact has an addition fact behind it.

  4. Read the table

    Read the table on the book page together, then alone.

  5. Cover and recall

    Cover the answers and ask the facts out of order.

  6. Story problems

    Read the problems aloud. They go like this:

    There are 13 pupils in school: if 3 of them leave, how many will remain?

    Charles had 15 marbles, and lost all but 5: how many did he lose?

    Your child answers in a full sentence.

  7. Wrap up

    Your child writes three facts from today's table from memory.

Afterwards

Two minutes a day on this table, mixed with the earlier ones.

Tip

Taking 10 away just removes the ten: 10 from 17 leaves 7.

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