Teaching mathematics
Teaching mathematics

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Teaching mathematics

2.1 Using number bonds to 10, 20, 100

Learning number bonds is an important skill which supports learners to be able to answer more difficult questions. For example, learning how to quickly calculate number bonds to 100 can help with bridging over 100.

A quick way of calculating 100 – 38 is to make the tens number up to 90 and the units number up to 10.

30 right arrow 90 postfix times normal i times normal s postfix times 60
eight right arrow 10 postfix times normal i times normal s postfix times two

So 38 right arrow 100 normal i times normal s postfix times 62

You can also say that 62 is the complement to 38.

Note that we have not used an ‘equals’ sign because these are not strictly mathematical sentences but they mirror what the learner may be saying in their head or aloud.

Similar quick ways can be used to find numbers that sum to 1000. For example, to work out 1000 – 159:

100 right arrow 900 postfix times normal i times normal s postfix times 800
50 right arrow 90 postfix times normal i times normal s postfix times 40
nine right arrow 10 postfix times normal i times normal s postfix times one

So 159 right arrow 1000 postfix times normal i times normal s postfix times 841 or 1000 minus 159 equals 841

This method also works for reckoning the change from £10.00.

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