Imagine I'm queuing up to buy four items of clothing, which cost £29.95, £49.95, £59.95 and £99.95. To pass time I decide to work out the mean price of these 4 items. To make the numbers easier to deal with, I add 5p to each amount and then divide by 10, giving me £3, £5, £6 and £10. It's very easy to work out the mean of these 'coded' prices in my head - it's £6. And now I can uncode that mean by multiplying by 10 then subtracting 5p (the inverse of the original coding). That quickly gives me the actual mean price of the clothes, which is £59.95.

**Resources**

Here's a few

**resources I've found for teaching this topic:**- Teachitmaths.co.uk has a lovely worksheet for helping pupils understand the affect of coding. Just beware of the error in the extension questions - both data sets should have six values, not five.
- Schoolworkout.co.uk has this sorting activity and this worksheet.
- Phildb on tes.co.uk has written this worksheet.

Hi Jo, the schoolworkout.co.uk link appears to be broken

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