NumihanaColumn subtraction with exchanging.
Align equal places. If there are too few units in a place, exchange one from a place to the left for ten in the next place. Exchanging changes the representation, not the number.
When this helps
Useful for written subtraction, including exchanging through a zero placeholder.
A common slip
An exchange affects neighbouring places. Keep the adjusted values for the later columns.
Worked example
931 − 524 =
After exchanging, how many units are available in the ones place?
Exchange one tens for ten ones.
11What answer digit belongs in the ones place?
Subtract 4 from the available 11.
7What answer digit belongs in the tens place?
Subtract 2 from the available 2.
0What answer digit belongs in the hundreds place?
Subtract 5 from the available 9.
4What is the final answer?
Recombine your working and check it against the original question.
407
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Teaching context
This lesson practises mathematical representations and calculations. The displayed practice uses selected England Year 3 skills; the strategy can also help learners in other years.
Curriculum alignment describes the mathematical skill. It does not mean this is the only required teaching method.
Department for Education: mathematics programmes of study ↗Original method lesson v1.
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