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Shopping Maths

Maths hiding in shopping: unit prices

Compare cost per item in child-friendly language.

Quick answer

Maths hiding in shopping: unit prices helps you find the best deals by comparing how much each item costs per unit, like how much one apple costs or how much one litre of milk costs. This makes shopping smarter and saves money!

Learning outcome

By the end of this page, you will be able to compare unit prices to find the best value when shopping, so you know which item gives you more for your money. Success signs:
  • You can tell which item is the better deal by looking at the price per unit
  • You can calculate how much one item costs if you know the total price
  • You can spot when a big pack seems cheaper but isn’t really
  • You can use maths to save money when shopping with your parent or carer

Why this matters

Shopping is full of maths! When you're buying things, you're using maths to decide what's the best value. For example, if you're buying milk, you might see a 1-litre carton for £1 and a 2-litre carton for £1.80. Which one is better? That’s where unit prices come in. Understanding unit prices helps you make smart choices, save money, and feel like a shopping superstar!

How it works

To find the unit price, you divide the total cost by how many units you get. For example:
  1. Find the total price of the item
  2. Find how many units are in the pack (like how many apples, or how many litres)
  3. Divide the price by the number of units
  4. Compare the unit prices to see which one is cheaper

Examples you can see

Let’s imagine you’re at the shop and you want to buy some orange juice. You see two bottles:
  • Bottle A: 1 litre for £1.20
  • Bottle B: 2 litres for £2.20
To find out which one is better, you calculate the unit price:
  • Bottle A: £1.20 ÷ 1 litre = £1.20 per litre
  • Bottle B: £2.20 ÷ 2 litres = £1.10 per litre
So, Bottle B is cheaper! Even though it costs more in total, you get more juice for less money.

Try it as a mini adventure

Adventure: The Supermarket Detective You are a detective and your job is to find the best deals in the supermarket. You have a shopping list:
  • 12 eggs for £2.40
  • 6 apples for £1.50
  • 1 litre of milk for £1.00
You need to work out the unit price for each item to see which is the best value. Here’s how to solve it:
  1. Eggs: £2.40 ÷ 12 = £0.20 per egg
  2. Apples: £1.50 ÷ 6 = £0.25 per apple
  3. Milk: £1.00 ÷ 1 = £1.00 per litre
Now, you can compare them:
  • Eggs are £0.20 each
  • Apples are £0.25 each
  • Milk is £1.00 per litre
So, the eggs are the best deal! You’ve solved the mystery and saved money!

Common mistakes

  • Mistake: Thinking the bigger pack is always cheaper.
    Why it happens: Children often think that if a pack is bigger, it must cost less per item.
    Fix: Always calculate the unit price to check!
  • Mistake: Adding the prices instead of dividing.
    Why it happens: Confusing the steps in the calculation.
    Fix: Remember: to find the unit price, you divide the total price by the number of items.
  • Mistake: Not checking if the units are the same.
    Why it happens: Sometimes items are sold in different units (like grams and kilograms).
    Fix: Make sure both items are in the same unit before comparing.

Parent and carer guide

As a parent or carer, you can help your child by:
  • Letting them help you check unit prices when shopping
  • Using a calculator to make the division easier
  • Asking questions like: “Which one is cheaper?” or “How much does one apple cost?”
  • Encouraging them to compare prices when you're at the supermarket
  • Practising at home with items you already have
You don’t need to be a maths expert – just be patient and supportive. The more you do it together, the more confident your child will become!

Practice questions

  1. 15 pencils cost £3.00. How much does one pencil cost?
  2. 3 bags of chips cost £2.70. How much does one bag cost?
  3. 2 bottles of water cost £1.60. How much does one bottle cost?
  4. 10 stickers cost £1.50. How much does one sticker cost?
  5. 5 oranges cost £1.25. How much does one orange cost?
Answers:
  1. £3.00 ÷ 15 = £0.20 per pencil
  2. £2.70 ÷ 3 = £0.90 per bag
  3. £1.60 ÷ 2 = £0.80 per bottle
  4. £1.50 ÷ 10 = £0.15 per sticker
  5. £1.25 ÷ 5 = £0.25 per orange

FAQ

Why do we need to know unit prices?

Unit prices help you make smart choices when shopping. They let you know how much you’re really paying for one item, so you can save money and get the best deals.

Can I use unit prices for anything else?

Yes! You can use unit prices to compare anything, like how much one piece of cake costs or how much one sheet of paper costs. It’s a useful skill for everyday life.

How do I teach my child about unit prices?

Start with simple examples at home, like comparing the cost of 10 cookies vs 20 cookies. Use real shopping trips or play with store flyers. Let them do the calculations and talk through their thinking.

What if the units are different?

If the units are different, like one item is in grams and another in kilograms, convert them to the same unit first. For example, 1000g = 1kg. Then you can compare them properly.

Are unit prices always the same in every shop?

No, prices can be different in different shops. That’s why it’s good to compare prices and look for the best deals. You can even make a shopping list with prices from different shops to see where you save the most!