How to explain percentages to your child, even if you never learned them

If you never studied percentages, the word itself is intimidating. It should not be. A percentage is one idea, and you already use it every time you bargain in a shop.

The whole idea, in one sentence

Per cent means 'out of a hundred'. That is the entire concept. Everything else is arithmetic.

Take a hundred-rupee note. Fifty per cent of it is fifty rupees. Ten per cent is ten rupees. Your child can see this without any explanation at all — the note does the teaching.

Now make it work for any number

The trick that carries a child through every percentage question in school is this: find ten per cent first, because ten per cent is easy. Then build.

1. 1To find 10%, move the decimal point one place to the left. 10% of 240 is 24.
2. 25% is half of 10%. So 5% of 240 is 12.
3. 320% is double 10%. So 20% of 240 is 48.
4. 415% is 10% plus 5%. So 15% of 240 is 24 + 12 = 36.

Almost every percentage a school asks about can be built from tens, halves and doubles. Your child never needs to multiply by 0.15.

The sentence to say

Try this, word for word: 'Forget the question for a second. What is ten per cent of this number? Just move the point one step left. Good. Now, is fifteen more than ten or less? More. So we need ten, and then a bit more. Half of ten is five. Add them.'

One more trick, for free

Percentages can be flipped. 18% of 50 is hard. 50% of 18 is easy — it is 9. They are the same answer, always. If one direction looks difficult, turn it round.

Show your child that once and watch their face. That is the moment maths stops being a set of rules and starts being something you can be clever about.