Written subtraction is one of those areas of maths that children frequently get wrong, mainly because they do not fully understand the method. This page looks at 3-digit subtraction and all the questions need ‘decomposition’ in order to get them correct. The last three questions should be laid out in the same way as the questions above.
Watch out for when there is a zero on the top line; for example when faced with question one:
zero subtract six is not six.
Rather, say ‘zero take way six cannot be done so I need to borrow 10 from the tens column.’ (I don’t really like this phrase because zero take away six can be done: the answer is negative six, but this takes us into a completely different method of subtraction which I will discuss one day when it’s been raining all day!)
It is always a good idea to check the answer by adding the answer line to the line above, which, in turn should give you the number at the top of the question.
This page can be found in our Four Rules section, under subtraction.
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