Your Kid’s Math Homework · Chapter 4

Open Number Line

An open number line isn’t a ruler: it’s a record of the jumps you make in your head. Subtracting by counting up makes borrowing across zeros disappear.

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Opens on Chapter 4’s example: 82 − 37, counting up from 37: +3, +40, +2.

Enter the numbers from the worksheet, then press Show me.
From the book, Chapter 4. 82 − 37 by counting up: from 37 jump 3 to 40, then 40 to 80, then 2 to 82. The jumps add to the answer, 3 + 40 + 2. The same idea takes 503 − 298 to 2 + 200 + 3 with no borrowing at all.

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