# Maths - Below zero and beyond

"Why do we need to learn this? What use is it?" Here is what you could say if they're learning about negative numbers, writes Peter Hall.

It may be worth mentioning temperature. Why do we have a temperature scale with temperatures below zero? Why is zero where it is? Is it a good idea to discuss the rather arbitrary labelling on the Celsius scale? It is helpful to label the freezing and boiling points of water as 0 and 100, respectively, and you can construct a scale from there.

Or you could look at money. For some children, the idea of borrowing money and paying it back might help them to ground negative numbers in something a little less abstract.

In geography, sea levels are a reason to use negative numbers. Show some cross-sections from maps to emphasise the reason for negative numbers and help pupils to visualise journeys that start below the sea and finish above it.

Finally, there is a mathematical reason for negative numbers, to do with completeness. In the beginning, we want to count things, and we do lots of addition and multiplication, subtraction and division. Mathematically, we would like to have fractions so we can solve more multiplication problems, and negative numbers so we can solve more subtraction problems. If we're tempted to say "you can't take away 5 from 3", negative numbers give us a great way to solve that - and to offer a whole new universe of mathematics.

What else?

Lewi Hylton's PowerPoint provides an introduction to negative numbers. bit.lyNegNumbers

Help pupils to count their coins with the TES Money collection. bit.lyCountingCoins.

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