Magazine article Times Educational Supplement

Maths - How Not to Do Fractions: Resources

Magazine article Times Educational Supplement

Maths - How Not to Do Fractions: Resources

Article excerpt

It just doesn't add up for some children, but pizza can help ...

I have lost count of the number of times I have seen an answer like the one pictured above while marking an exam paper or a piece of homework. It does not seem to matter if the pupil in question is a fresh-faced Year 7 or a weary Year 11 who has been taught the topic annually for several years - when pupils are asked to add up two fractions, they confidently, and without a second thought, add the tops and the bottoms.

More worryingly still, some pupils offer a justification for their answer: "Well, if I got one out of three in the first test and one out of five in the second test, then I have scored two out of eight overall."

What's the solution?

This is a difficult one. Pupils have so many facts and rules swarming around in their heads about angles, algebra and averages that, when they are faced with something as simple as a plus sign, they just cannot resist using it in the way they were taught back in the days when maths was easy.

I think the only hope is to show them their answer simply cannot be right. I start by asking pupils which is bigger: one-third or one-quarter. After a brief discussion about pizza or cake, most are happy that a third is the larger option. I then ask them if they can simplify the answer of two- eighths. After slicing up the pizza a few more times, we reach the stage where we are happy that it is the same as one-quarter. Now I pause and ask the pupils if they are happy with what is written on the board. …

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