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Spy maths quest: subtraction

Maths Adventures

Spy maths quest: subtraction

A story-led junior maths adventure using codes, gadgets and secret missions to work out what is left after trades, rescues or escapes.

Quick answer

Subtraction is like taking away or finding what is left. When you have a secret mission and need to work out how many gadgets you still have after using some, or how many people are left after some escape, you use subtraction.

Learning outcome

By the end of this page, you will be able to subtract numbers up to 20 to solve spy missions, like working out how many secret codes are left after using some, or how many friends are still hiding after some have been found. Success signs:

You can take away objects or numbers and find how many are left
You can solve simple subtraction problems with numbers up to 20
You can imagine or draw subtraction problems like a spy
You can use subtraction to solve real-life spy missions

Why this matters

Subtraction helps you solve puzzles, find clues, and keep secrets safe. In spy missions, you might have 10 secret gadgets and use 3 of them. You need to know how many gadgets are left. This is subtraction! It's also useful when sharing snacks, counting down to a party, or working out how many people are still hiding in a game.

How it works

Subtraction means taking away or finding what is left. You can think of it like:

Starting with a group of things
Using or taking away some of them
Finding how many are left

Example: If you have 8 spy glasses and use 3 of them, you have 5 left.

Start with: 8 glasses
Use: 3 glasses
Left: 8 - 3 = 5 glasses

Examples you can see

Let's imagine you are a spy with a secret mission. Here are some examples of subtraction in action: Example 1: The Secret Code You have 12 secret codes to crack. You crack 5 of them. How many are left?

Start with: 12 codes
Crack: 5 codes
Left: 12 - 5 = 7 codes

Example 2: The Spy Escape You are hiding with 9 friends. 4 friends escape to safety. How many are still hiding?

Start with: 9 friends
Escape: 4 friends
Still hiding: 9 - 4 = 5 friends

Example 3: The Gadget Trade You trade 6 gadgets for 2 new ones. You had 10 gadgets. How many do you have now?

Start with: 10 gadgets
Trade away: 6 gadgets
Get: 2 gadgets
Now have: 10 - 6 + 2 = 6 gadgets

Example 4: The Mission Time Your mission takes 15 minutes. You've already spent 8 minutes. How much time is left?

Start with: 15 minutes
Spent: 8 minutes
Left: 15 - 8 = 7 minutes

Try it as a mini adventure

Spy Mission: The Missing Files You are a spy with 12 secret files. You need to hide them in different places. You hide 3 files in the safe, 4 files in the drawer, and 2 files under the rug. How many files are left to hide?

Start with: 12 files
Hide in safe: 3 files
Hide in drawer: 4 files
Hide under rug: 2 files
Total hidden: 3 + 4 + 2 = 9 files
Left to hide: 12 - 9 = 3 files

4th time: ? files are left to hide Challenge: The Spy Escape Route You have 10 secret paths to escape. You take 3 paths to the car, 2 paths to the park, and 1 path to the river. How many paths are left to take?

Start with: 10 paths
Car: 3 paths
Park: 2 paths
River: 1 path
Used paths: 3 + 2 + 1 = 6 paths
Left to take: 10 - 6 = 4 paths

4th time: ? paths are left to take

Common mistakes

Mistake: Thinking 10 - 3 = 7, but getting confused when the numbers are bigger. Why it happens: Not counting carefully or not understanding the "take away" concept. Fix: Use your fingers, draw pictures, or count backwards from the bigger number.
Mistake: Confusing the order of subtraction. Why it happens: Not knowing that 10 - 3 is different from 3 - 10. Fix: Always start with the bigger number when taking away.
Mistake: Forgetting to count how many are left. Why it happens: Rushing or not reading the problem carefully. Fix: Read the problem twice and check how many are left after taking some away.

Parent and carer guide

You can help your child by:

Playing subtraction games like "Take Away" with toys or snacks
Using real-life situations like sharing cookies or counting down to bedtime
Encouraging them to draw pictures of subtraction problems
Practising with simple subtraction problems like 8 - 3 = ?
Not worrying if they make mistakes - they are learning!

What to say: "Let's count how many you started with." "Can you show me how many are left?" "Try counting backwards from the bigger number." What not to worry about: Your child may not get all answers right away. That's normal. Keep it fun and keep practising.

Practice questions

There are 10 spy glasses. You use 4. How many are left?
You have 15 secret messages. You send 6. How many are left?
There are 12 gadgets. You trade 5. How many do you have now?
You have 18 files. You hide 9. How many are left?
There are 14 friends. 7 escape. How many are left?

Answers:

10 - 4 = 6 glasses
15 - 6 = 9 messages
12 - 5 = 7 gadgets
18 - 9 = 9 files
14 - 7 = 7 friends

FAQ

What is subtraction?

Subtraction is taking away or finding what is left after you use some of something.

How can I practice subtraction?

You can practice by counting backwards, using toys or snacks, or drawing pictures of problems.

Why do we use subtraction?

We use subtraction to find out how many are left after we use or take some away.

What are some real-life examples of subtraction?

Sharing snacks, counting down to a party, or working out how many people are still hiding in a game.

How can I help my child with subtraction?

You can help by playing games, using real objects, and encouraging them to draw pictures of subtraction problems.