Your child comes back from the shop and asks: '30% off a chocolate bar — how many pence is that, actually?' If you also paused for a second to work it out, this article is for you — and for them.
When your child comes home with a test marked 80 out of 100, you understand straight away that they scored 80%. When you see a '30% off' sign in the supermarket, you know something needs working out — but it is not always obvious exactly what. Percentages are everywhere in everyday life, which is why they are a central topic in the Year 6 curriculum and turn up every year in the KS2 SATs. This article is here to help you explain the topic to your child in a simple way, with examples they already know from life.
What is a percentage, anyway?
The word 'per cent' means 'out of a hundred'. When we say 'one per cent', we split the whole amount into exactly 100 equal parts and take one of them. That is the only rule you need to remember.
Picture a round pizza cut into 100 equal slices. Each slice is 1%. 25% is 25 slices — a quarter of the pizza. 50% is half. 100% is the whole pizza. It really is that simple.
How to find a percentage of an amount
The basic formula is: percentage × amount ÷ 100. Let's go straight to some real-life examples.
- What is 10% of £50? 50 ÷ 100 = 0.5, then × 10 = £5. So 10% of £50 is £5.
- What is 30% off a chocolate bar costing £1.20? 1.20 ÷ 100 = 0.012, then × 30 = £0.36 — that is how much you save. The price after the discount: 1.20 − 0.36 = £0.84.
- VAT in the UK is 20%. If an item costs £100 before VAT, the VAT is £20 and the final price is £120.
- Your child got 80% in a spelling test. That means they answered 80% of the questions correctly. If there were 50 questions, they got 50 × 80 ÷ 100 = 40 right.
The 10% trick — a real time-saver
10% of any number = divide by 10. That is easy to do in your head. From 10% you can build almost every common percentage: 5% is half of 10%, 20% is double 10%, 30% is three lots of 10%, 15% is 10% + 5%. When you are in the supermarket and see '30% off crisps at £1.00': 10% of £1.00 is 10p, so 30% is 30p. Price after the discount: 70p.
How fractions, decimals and percentages connect
A percentage, a fraction and a decimal are three ways of writing exactly the same thing. The table below shows the most common equivalences a Year 6 child should know by heart:
| Percentage | Fraction | Decimal | Real-life example |
|---|---|---|---|
| 1% | 1/100 | 0.01 | one penny in a pound |
| 10% | 1/10 | 0.1 | a reasonable tip in a restaurant |
| 20% | 1/5 | 0.2 | VAT in the UK |
| 25% | 1/4 | 0.25 | a quarter of the price |
| 33% | 1/3 | 0.33 | a third (roughly) |
| 50% | 1/2 | 0.5 | half price |
| 75% | 3/4 | 0.75 | three quarters |
| 100% | 1/1 | 1 | the full price — the whole |
It is worth sticking this table on the fridge. A child who knows it by heart saves a lot of time in tests — and in real life.
Discounts and price rises — maths that matters
Discounts are where percentages become genuinely interesting to children — because real money is involved. Prices in the shops are full of percentage offers, and it is worth teaching children to work them out in their heads.
Discount: new price = old price × (100 − discount %) ÷ 100
Example: a T-shirt costs £120 and has 25% off. What is the sale price? Work it out: 120 × (100 − 25) ÷ 100 = 120 × 75 ÷ 100 = 120 × 0.75 = £90. The short way: 25% of 120 = £30. 120 − 30 = £90.
Price rise: new price = old price × (100 + increase %) ÷ 100
VAT is really a price rise. An item at £200 before VAT — the price with 20% VAT is: 200 × 120 ÷ 100 = £240. When you shop on the high street, the price you see already includes VAT — but knowing how to add it is useful for trade prices and online quotes.
A child who can work out percentages in their head will be a smarter shopper for life.
What '100% of something' means — the whole
100% is always the whole — the full amount, before any change. If a child ate 100% of the pizza, they ate all of it. If they scored 100% in a test, they got everything right. It is important to understand that you can also have more than 100%: if a price went up by 200%, it tripled. 100% is the original, plus another 200%, makes three times as much altogether.
Reverse problems — finding the original price
This is the part children (and not only children) find hardest. A reverse problem is when you know the result and want to find where you started.
The classic example: sale price → original price
Your child paid £60 after a 25% discount. What was the original price? It is wrong to find 25% of 60 and add it back — that is a very common mistake! The correct way: after a 25% discount, 75% of the price is left. So £60 = 75% of the original price. 1% = 60 ÷ 75 = £0.80. 100% = 0.80 × 100 = £80. The original price was £80.
Another example: scores and questions
In a test with 40 questions, your child scored 85%. How many questions did they get right? 40 × 85 ÷ 100 = 34 questions. The other way round: your child got 34 out of 40. What percentage is that? 34 ÷ 40 × 100 = 85%. Both routes lead to the same place.
Common mistakes worth knowing about
- Subtracting percentages from each other: you cannot simply add up different percentage discounts. 20% off followed by another 10% off is not 30% off altogether — it is 28% (because the second 10% is worked out on the price after the first 20%).
- Reverse problems: working out X% of the sale price to get back to the original is wrong. You have to work from 100% minus the discount.
- Confusing 'reduced by 50%' with 'is 50% of the price': these are the same thing — the new price is half.
- Multiplying without dividing by 100: don't forget the ÷ 100. 30 per cent of 200 = 200 × 30 ÷ 100 = 60, not 6000.
- Forgetting VAT is already included: on the high street almost every price you see already includes VAT. You do not add another 20% on top.
How to practise percentages in everyday life
The best way to make percentages stick is to practise in real situations, not only on a worksheet. Here are some ideas that work:
- In the supermarket: let your child work out how much each offer saves before you reach the till.
- On a restaurant bill: practise working out a 10% and a 12.5% tip on the total.
- In football and other sports: what percentage of matches did the team win? What percentage of shots did the goalkeeper save?
- On the school report: work out together what the average is as a percentage out of 100 and where there is room to improve.
- On the energy bill: explain what a 5% price rise means and how it changes the monthly payment.
The key is to turn maths into a natural conversation, not a lesson. When a child feels that maths is relevant to their life, the motivation to practise goes up noticeably.
Frequently asked questions
What is the difference between a percentage and a fraction?
A percentage is a fraction whose denominator is always 100. 30% = 30/100 = 3/10. It is the same amount, just written differently. Percentages are easier to compare because everything is on a common base — a hundred.
How do you explain percentages to a Year 6 child simply?
The best way is through shop discounts: 'If a chocolate bar costs £1.00 and has 30% off, how much will you pay?' First find 10% = 10p, so 30% = 30p, and the final price is 70p. Examples with real money help enormously.
What is VAT and how do you work it out?
VAT (value added tax) in the UK is 20% on most goods. That means for an item costing £100 before VAT, you add £20 and the final price is £120. Most prices in shops already include VAT.
How do you find the price before a discount if you know the price after?
If you paid £75 after a 25% discount, then £75 is 75% of the original price. Work out: 75 ÷ 75 × 100 = £100. One rule: divide the amount paid by the percentage that is left (100 minus the discount) and multiply by 100.
When are percentages taught in schools in England?
Percentages are introduced in Year 5 of the national curriculum (recognising the % symbol and simple equivalences) and developed properly in Year 6, where children find percentages of amounts and connect them with fractions and decimals. They appear in the KS2 SATs reasoning papers and are extended at KS3 to percentage change and reverse percentages.
How can I help a child who struggles with percentages?
Start with 10% only — it is always dividing by 10. Once that is fluent, move to 20%, 30% and so on. Avoid abstract formulae at first; work with round numbers and real-life examples. MathsUK offers percentage practice matched to Year 6 with instant feedback.
Do you need to know percentages by heart for GCSE?
Yes — percentages are a foundation topic that appears in GCSE maths, science and business studies. Being secure in Year 6 saves a lot of work later. These come up most often: simple interest, price discounts, percentage change and reverse percentages.
What is the difference between 'reduced by 50%' and 'reduced to 50%'?
'Reduced by 50%' means half the price was taken off — the final price is 50% of the original. 'Reduced to 50%' means exactly the same thing — the price is now 50% of the original. Although they sound different, both phrases describe the same outcome. The distinction matters more with increases: 'up by 50%' is not the same as 'up to 50%'.
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