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Maths Adventures

Castle maths quest: subtraction

A story-led junior maths adventure using towers, walls and dragon-proof designs to work out what is left after trades, rescues or escapes.

Quick answer

Subtraction is about taking away or finding what is left. When you have 10 dragons and 3 fly away, you have 7 left. You can use subtraction to work out how many are missing, how much is left, or how much you need to take away.

Learning outcome

By the end of this page, you will be able to use subtraction to solve problems about taking away, finding what is left, or comparing amounts in your everyday life. Success signs:
  • You can take away objects or numbers and find what is left
  • You can use subtraction to solve story problems
  • You can show subtraction with drawings or objects
  • You can check your subtraction answers

Why this matters

Subtraction is like being a detective in a castle. When you have a treasure chest with 15 gold coins and you give 6 to your friend, you need to subtract to find out how many coins are left. In real life, subtraction helps you know how much money you have left after buying something, how many friends are still at play, or how many bricks you need to build your tower. In games and adventures, subtraction helps you work out how many lives you have left, how many points you need to win, or how many steps you still need to climb. Subtraction is used in cooking, sports, and even in making music!

How it works

Subtraction means taking away or finding what is left. It uses the minus sign (–) and the equals sign (=). Here’s how to think about it:
  1. Start with a number (this is called the minuend)
  2. Take away a smaller number (this is called the subtrahend)
  3. Find what is left (this is called the difference)
For example: 8 – 3 = 5. You start with 8, take away 3, and you have 5 left. You can also think of subtraction as:
  • Counting backwards
  • Comparing two amounts
  • Checking how much is missing

Examples you can see

Let’s imagine you are in a castle with towers, walls, and dragons. Here are some examples: Example 1: Dragons in the sky You see 12 dragons flying over the castle. 5 dragons fly away. How many dragons are left? We write: 12 – 5 = 7 You can draw 12 dragons, cross out 5, and count the 7 left. Example 2: Building blocks You have 20 blocks to build a wall. You use 12 blocks. How many blocks are left? We write: 20 – 12 = 8 You can use 20 counters or cubes, take away 12, and count the 8 left. Example 3: Dragon food You have 15 pieces of dragon food. You eat 9 pieces. How many pieces are left? We write: 15 – 9 = 6 You can draw 15 food pieces, eat 9, and count 6 left. Example 4: Castle guards There are 8 guards at the gate. 3 guards go to the tower. How many guards are left at the gate? We write: 8 – 3 = 5 You can use 8 toy soldiers, move 3 to another spot, and see 5 left.

Try it as a mini adventure

Castle Rescue Quest You are a brave knight in a castle. You have 16 magic stones to protect your tower. But you need to give 7 stones to your friend who is helping with the dragon-proof walls. How many stones do you have left? 4th time: You have 16 stones. 5th time: You give away 7 stones. 6th time: You need to find how many are left. Answer: 16 – 7 = 9 stones left. Mini challenge: You find 10 more stones in the treasure room. How many stones do you have now? Answer: 9 + 10 = 19 stones Another quest: Your friend gives you 5 more stones. How many do you have now? Answer: 19 + 5 = 24 stones Final challenge: You must use 12 stones to build a new gate. How many stones are left? Answer: 24 – 12 = 12 stones

Common mistakes

  • Mistake: Thinking 10 – 3 = 13 instead of 7. Why: Confusing subtraction with addition. Fix: Use counters or draw to see the difference. 10 – 3 means take away 3 from 10, so you get 7.
  • Mistake: Writing 15 – 8 = 7 instead of 7. Why: Not counting carefully. Fix: Count backwards from 15: 14, 13, 12, 11, 10, 9, 8. That’s 7 steps, so 15 – 8 = 7.
  • Mistake: Subtracting the bigger number from the smaller number. Why: Not understanding which number is the starting amount. Fix: Always ask, “What is the bigger number?” That’s your starting number.
  • Mistake: Forgetting to write the minus sign. Why: Not paying attention to the symbols. Fix: Always look for the – sign and make sure you have the equals sign too.

Parent and carer guide

You can help your child with subtraction by:
  • Using everyday situations: “You had 10 cookies and ate 3. How many are left?”
  • Playing subtraction games with counters, blocks, or toys
  • Using visual aids like drawing or number lines
  • Practising with simple number sentences
  • Checking answers with addition (if 10 – 3 = 7, then 7 + 3 = 10)
Remember: It's okay if your child makes mistakes. They are learning! Encourage them to try again and explain their thinking.

Practice questions

  1. There are 12 apples. You eat 5. How many apples are left? Answer: 7
  2. You have 18 coins. You spend 9. How many coins do you have left? Answer: 9
  3. There are 15 birds in a tree. 6 fly away. How many birds are left? Answer: 9
  4. You start with 20 bricks. You use 11. How many bricks are left? Answer: 9
  5. There are 14 candles on a cake. 8 are blown out. How many candles are still lit? Answer: 6
  6. You have 16 toy soldiers. 7 are in the castle. How many are outside? Answer: 9
  7. You start with 25 stars. You give 13 to your friend. How many stars do you have left? Answer: 12
  8. There are 17 fish in a pond. 9 swim away. How many fish are left? Answer: 8
  9. You have 22 sweets. You eat 6. How many sweets are left? Answer: 16
  10. There are 13 balloons. 4 pop. How many balloons are left? Answer: 9

FAQ

What is subtraction?

Subtraction is taking away or finding what is left when you take one number from another.

How do I know which number to subtract from which?

The bigger number usually goes first. For example, 10 – 3 means you start with 10 and take away 3.

Why do we use subtraction?

We use subtraction to find out how much is left, how many are missing, or how much one thing is more than another.

Can I use subtraction with big numbers?

Yes! You can subtract any numbers, even large ones. For example, 100 – 25 = 75.

How can I practice subtraction at home?

You can practice by counting objects, using coins, playing subtraction games, or solving story problems with everyday items like food or toys.