Maths hiding in shopping: discount signs

Quick answer

Discount signs show how much money you save when you buy something during a sale. You can work out the savings by finding a percentage of the original price. For example, if something costs £10 and is 25% off, you save £2.50.

Learning outcome

By the end of this page, you will be able to calculate how much money you save when something is marked down by 10%, 25%, or 50%.

• You can find 10% of any number
• You can find 25% of any number
• You can find 50% of any number
• You can work out how much you save when shopping

Why this matters

Shopping maths helps you understand how much you are saving when things go on sale. It's useful for real-life situations like:

• Planning your pocket money
• Helping parents budget for family shopping
• Playing games where you earn or spend money
• Understanding how prices change in shops

Knowing how to calculate discounts makes you a smart shopper and helps you make better choices about spending your money.

How it works

When you see a discount sign, it tells you how much less you will pay. Here's how to work it out:

1. First, find the original price of the item
2. Then, work out what percentage is being taken off
3. Next, calculate that percentage of the original price
4. Finally, subtract the savings from the original price

For example, if a toy costs £8 and is 25% off:

1. Original price = £8
2. Discount = 25%
3. 25% of £8 = £2
4. Final price = £8 - £2 = £6

Examples you can see

Let's look at some simple examples using different percentages:

10% off

When something is 10% off, you save one-tenth of the price.

25% off

When something is 25% off, you save one-quarter of the price.

50% off

When something is 50% off, you save half the price.

Try it as a mini adventure

Imagine you are on a shopping trip with your family. You have £20 to spend and want to buy something special for your birthday. You find a toy that costs £16. It's 25% off. How much will you save? How much will you pay?

1. Original price = £16
2. Discount = 25%
3. Find 25% of £16 = ?
4. How much do you save? = ?
5. How much do you pay? = ?

Let's solve it together:

1. 25% of £16 = £4
2. You save £4
3. Final price = £16 - £4 = £12

You can also try this challenge: If you have £15 and find a book that costs £20 but is 25% off, can you afford it? What will you pay?

Common mistakes

• Mistake: Thinking 25% off means you pay 25% of the price. Why it happens: Children often confuse "off" with "pay". Fix: Remember, 25% off means you save 25%, so you pay the remaining 75%.
• Mistake: Adding the percentage to the price instead of finding a fraction of it. Why it happens: Confusion between percentages and addition. Fix: Always find the percentage of the original price, not add it to the price.
• Mistake: Forgetting that 50% is the same as half. Why it happens: Not connecting percentages to familiar fractions. Fix: Remember: 50% = ½, 25% = ¼, 10% = 1/10.

Parent and carer guide

Helping your child with shopping maths can be fun and practical:

• Point out discount signs while shopping and ask your child to calculate savings
• Use real items at home to practice calculating percentages
• Play a game: "What's the savings?" when you see a sale
• Let your child help you budget for a family shopping trip
• Ask questions like: "How much would you save if something costs £12 and is 25% off?"
• Don't worry if they make mistakes - they're learning!
• Use simple language and relate it to things they already know
• Make it a game - the more you practice, the more confident they'll become
• Encourage them to show their working, even if it's with drawings or counters
• Remember that 10% is just one-tenth, 25% is one-quarter, and 50% is half

Practice questions

1. How much do you save if a £10 toy is 10% off?
2. What is 25% of £16?
3. A £20 jumper is 50% off. How much do you save?
4. How much will you pay for a £24 book that is 25% off?
5. What is 10% of £30?

Answers

1. £1
2. £4
3. £10
4. £18
5. £3

FAQ

What does 10% mean?

10% means one-tenth. If something costs £10, 10% of that is £1.

How do I calculate 25% of a number?

25% means one-quarter. You can divide by 4 or find one-quarter of the number.

Why is 50% the same as half?

Because 50% means 50 out of 100, which is the same as ½.

Can I use a calculator for percentages?

Yes! But it's good to know how to do it by hand first so you understand what's happening.

How can I practice more?

You can practice by looking at sale signs, playing money games, or calculating discounts on items you like to buy.