Use a Known Double for a Near Double

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 7+8, use 7+7=14 and add one more: 15.
• All quantities and shape descriptions are supplied in the worked example and questions; no purchase or personal information is needed.

Learn the idea

A double joins two equal amounts. A near double has one part just one larger than the other. Start with the known double and account for the one extra object. This is a way to explain the fact, not only memorize its answer.

Double the smaller addend, then add the extra one. Write the double and the adjustment. Check that your two original addends differ by exactly one before using this particular shortcut.

Confirm the addends differ by one. A near double includes one more than the exact double. Draw two rows of the smaller number and one extra mark beside the second row.

1. Draw two rows of the smaller number and one extra mark beside the second row.
2. Follow the worked example. Point to each number or shape feature and say what it tells you.
3. Double the smaller addend, then add the extra one.
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 8+9. Expected: 16+1=17.

Nothing here is saved to an account or sent to a teacher. The answer download includes your current choice and any checked feedback. It does not include choices from the separate More practice section. Download that section separately.