Subtract in Two Parts Through Ten

Supplied materials

• Paper and a pencil; drawing and spoken explanations are welcome. An adult may read directions and options aloud.
• Supplied worked-case record: For 14−6, remove four to reach ten.
• All quantities and shape descriptions are supplied in the worked example and questions; no purchase or personal information is needed.

Learn the idea

Subtracting across ten can be split into a first removal that reaches ten and a second removal of the remainder. The two removed parts must add to the original subtraction amount. This connects the calculation to a visible full ten.

Remove enough from the teen start to reach ten. Work out how much of the requested removal remains, then remove that amount from ten. Check by adding the final result and the full removed amount.

Keep track of how much has already been removed. Do not remove the entire subtrahend again after reaching ten. Draw a teen as ten and extras; cross out the extras before the remaining removal.

1. Draw a teen as ten and extras; cross out the extras before the remaining removal.
2. Follow the worked example. Point to each number or shape feature and say what it tells you.
3. Remove enough from the teen start to reach ten.
4. Try the question and then the three practice questions. Check your answers and explain any change you make.

Check your reasoning

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Take it further

Find 16−9. Expected: 16−6−3=7.

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