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Maths Adventures

Detective maths quest: subtraction

A story-led junior maths adventure using evidence, charts and mystery patterns to work out what is left after trades, rescues or escapes.

Quick answer

Subtraction is like taking away or finding what's left. When you have a group of things and take some away, you use subtraction to find how many are left.

Learning outcome

By the end of this page, you will be able to use subtraction to solve detective mysteries by finding what is left after things are taken away, traded, or changed. Success signs:
  • You can subtract numbers up to 20 using objects or pictures
  • You can find the difference between two numbers
  • You can solve detective-style subtraction problems
  • You can explain how subtraction helps you solve puzzles

Why this matters

Subtraction is like being a detective! In real life, you use subtraction all the time. When you eat 3 cookies from a jar of 10, you subtract to find out how many are left. When you're planning a party and have 12 balloons but 4 pop, you subtract to see how many you still have. Subtraction helps you solve mysteries, count things, and make plans. It's used in games, cooking, sports, and even in space missions when scientists figure out how much fuel is left in a rocket.

How it works

Subtraction is the opposite of addition. Instead of putting things together, you take them apart. When you see a subtraction problem like 8 - 3, you start with 8 things and take away 3. The answer is what's left. You can think of subtraction as:
  1. Starting with a group of things
  2. Removing some of them
  3. Finding how many are left

Examples you can see

Let's imagine you're a detective solving a mystery about a treasure hunt. Example 1: You start with 15 gold coins in a chest. You give 6 coins to your friend. How many coins are left?
  • Start with: 15 coins
  • Take away: 6 coins
  • Left: 15 - 6 = 9 coins
Example 2: You find 20 puzzle pieces but lose 7 of them. How many pieces do you still have?
  • Start with: 20 pieces
  • Take away: 7 pieces
  • Left: 20 - 7 = 13 pieces
Example 3: A robot starts with 12 batteries but uses 5. How many batteries are left?
  • Start with: 12 batteries
  • Take away: 5 batteries
  • Left: 12 - 5 = 7 batteries

Try it as a mini adventure

Adventure: The Mystery of the Missing Numbers You are a detective in a magical school where numbers are disappearing from the blackboard! Your mission is to find out how many numbers are left after each mystery. Step 1: You see 10 numbers on the board. 3 numbers vanish during the night. How many are left?
  • Start: 10 numbers
  • Take away: 3 numbers
  • Left: ?
Step 2: You find 15 numbers in a box. 9 numbers are eaten by a hungry monster. How many numbers are left?
  • Start: 15 numbers
  • Take away: 9 numbers
  • Left: ?
Step 3: You collect 18 numbers from different rooms. 4 numbers get lost in a magic spell. How many numbers do you have now?
  • Start: 18 numbers
  • Take away: 4 numbers
  • Left: ?
Step 4: You start with 20 numbers. 12 numbers get mixed up in a puzzle. How many numbers are still clear?
  • Start: 20 numbers
  • Take away: 12 numbers
  • Left: ?
Step 5: You discover 25 numbers in a treasure chest. 10 numbers are hidden in a secret code. How many numbers are still visible?
  • Start: 25 numbers
  • Take away: 10 numbers
  • Left: ?

Common mistakes

  • Mistake: Thinking that 10 - 3 = 13
    Why it happens: Mixing up subtraction with addition
    Fix: Count backwards from 10: 9, 8, 7. So 10 - 3 = 7
  • Mistake: Starting with 8 and taking away 10
    Why it happens: Not understanding that you can't take away more than you have
    Fix: Remember: you can't take away more than what you start with
  • Mistake: Confusing "how many more" with "how many less"
    Why it happens: Not understanding the question fully
    Fix: Read the question carefully and think about what's being taken away
  • Mistake: Writing 5 - 2 = 3 but then saying "I need 5 more to get back to 5"
    Why it happens: Confusing subtraction with addition
    Fix: Remember that subtraction finds what's left, not what you need to add back

Parent and carer guide

Subtraction is a big part of everyday life. You can help your child by:
  • Using everyday situations like sharing food or toys to show subtraction
  • Letting them count backwards to solve problems
  • Using objects like coins, blocks, or counters to make subtraction visual
  • Practising with simple problems like "If you have 8 apples and eat 3, how many are left?"
  • Encouraging them to explain their thinking when solving problems
  • Not worrying if they make mistakes - they're part of learning!
  • Reassuring them that it's okay to use fingers or draw pictures to help

Practice questions

  1. There are 12 birds in a tree. 5 birds fly away. How many birds are left?
  2. You have 18 stickers. You give 6 to your friend. How many stickers do you have now?
  3. There are 20 stars in the sky. 8 stars disappear. How many stars are still visible?
  4. There are 15 pencils in a box. 9 pencils are used. How many pencils are left?
  5. You find 25 coins. 12 coins are taken by a friendly monster. How many coins do you still have?
Answers:
  1. 12 - 5 = 7 birds
  2. 18 - 6 = 12 stickers
  3. 20 - 8 = 12 stars
  4. 15 - 9 = 6 pencils
  5. 25 - 12 = 13 coins

FAQ

What is subtraction?

Subtraction is when you take away some things from a group to find how many are left.

How can I practice subtraction?

You can practice by using objects like toys, counting backwards, or solving everyday problems like "If I have 10 cookies and eat 3, how many are left?"

Why do I need to learn subtraction?

Subtraction helps you solve problems in daily life, like sharing food, planning parties, or figuring out how much time is left.

What's the easiest way to subtract?

Start by using objects, then count backwards, and finally try to remember the facts.

What if I make a mistake?

Mistakes are part of learning. When you make a mistake, try again and think about what went wrong.