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Leftovers maths mission

A junior real-world challenge using leftovers to practise subtraction without feeling like a worksheet.

Quick answer

Leftovers maths mission is a fun way to practice subtraction by working out how many items are left after sharing or eating. You can use it when you have leftover food, toys, or anything you're sharing with friends or family.

Learning outcome

By the end of this page, you will be able to solve subtraction problems using real-life situations like sharing food or toys, and work out how many are left over. Success signs:
  • You can count how many items are left after some are taken away
  • You can use subtraction to solve everyday problems
  • You can explain how subtraction helps you share fairly
  • You can make up your own leftover subtraction story

Why this matters

Leftovers maths is useful because it helps you understand how sharing works in real life. Whether you're dividing up snacks, splitting toys, or working out how much food is left, subtraction helps you know what's fair and how much is left over. This skill will help you in school maths, in games, and in everyday life when you need to share or decide what's left.

How it works

Leftovers maths works like this:
  1. Start with a total number of items (like 12 cookies)
  2. Take away or share some of them (like 5 cookies are eaten)
  3. Count how many are left (12 minus 5 equals 7 cookies)
This is subtraction in action! You can use your fingers, draw pictures, or use objects to help you work out the answer.

Examples you can see

Let’s imagine you are having a party and you have 10 cupcakes. You give 3 to your friend. How many are left? You can solve this by:
  • Starting with 10 cupcakes
  • Sharing or giving away 3 cupcakes
  • Counting how many are left: 10 – 3 = 7 cupcakes
Another example: You have 15 stickers and you give 6 to your little brother. How many do you have left?
  • Start with 15 stickers
  • Give away 6 stickers
  • Count the rest: 15 – 6 = 9 stickers
Here is a table showing how this works with different numbers:
Total items Items taken away Leftover items
10 3 7
15 6 9
8 2 6
12 5 7

Try it as a mini adventure

Adventure: The Great Leftover Challenge You are a chef in a big kitchen. You made 20 delicious cookies for the school bake sale. Your friends came and took some cookies to try. Here’s what happened:
  1. First friend took 4 cookies
  2. Second friend took 3 cookies
  3. Third friend took 5 cookies
  4. Fourth friend took 2 cookies
Now, you need to find out how many cookies are left for the sale. Step-by-step challenge:
  1. Start with 20 cookies
  2. Take away 4 cookies: 20 – 4 = ?
  3. Take away 3 more cookies: ? – 3 = ?
  4. Take away 5 more cookies: ? – 5 = ?
  5. Take away 2 more cookies: ? – 2 = ?
Can you work out how many cookies are left for the sale?

Common mistakes

  • Mistake: Thinking that 15 – 7 = 8 instead of 8.
    Why it happens: Kids might add the numbers instead of subtracting.
    Fix: Use objects like counters or draw pictures to count backwards.
  • Mistake: Forgetting to take away the correct number.
    Why it happens: Kids might get distracted or not read the problem carefully.
    Fix: Read the problem twice and use fingers or a number line to help.
  • Mistake: Mixing up "how many are left" with "how many were taken".
    Why it happens: Confusion between the total and the subtraction.
    Fix: Ask yourself, "What was the start number?" and "What was taken away?"

Parent and carer guide

Parents and carers can help by:
  • Using everyday situations to practice subtraction (like sharing food or toys)
  • Letting children count out objects to solve problems
  • Encouraging children to explain their thinking
  • Practising with a number line or counting backwards
  • Not worrying if children make mistakes – they’re learning!
Five-minute help tips:
  1. Ask your child to tell you a story about sharing food or toys
  2. Use a small pile of counters or toys to act out subtraction
  3. Practice subtraction with numbers up to 20
  4. Use a number line to help with counting backwards
  5. Ask your child to explain how they solved a problem

Practice questions

  1. You had 12 eggs and used 5 for baking. How many eggs are left?
  2. There were 18 pencils in the box. You gave 9 to your friend. How many are left?
  3. You had 14 balloons and 6 popped. How many are left?
  4. There were 16 apples and you ate 4. How many are left?
  5. You had 20 stickers and gave 7 to your sister. How many are left?
Answers:
  1. 12 – 5 = 7 eggs
  2. 18 – 9 = 9 pencils
  3. 14 – 6 = 8 balloons
  4. 16 – 4 = 12 apples
  5. 20 – 7 = 13 stickers

FAQ

What is the leftovers maths mission?

The leftovers maths mission is a fun way to practice subtraction using real-life situations like sharing food or toys. You work out how many items are left after some are taken away.

How can I use this at home?

You can use it when sharing snacks, toys, or anything you're dividing up. Try asking questions like, "How many cookies are left after we eat 3?" or "How many crayons do you have now?"

Why is subtraction important?

Subtraction helps us know how much is left when we share, eat, or use things. It's useful in everyday life and helps with more advanced maths in school.

Can I use this with younger children?

Yes! You can start with small numbers and use physical objects like toys or counters to help them understand how subtraction works.

How can I make it more fun?

You can turn it into a game, make up stories, or use your child’s favourite toys or food to make the problems more interesting and engaging.