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Maths Adventures

Sailing maths quest: subtraction

A story-led junior maths adventure using maps, bearings and voyage planning to work out what is left after trades, rescues or escapes.

Quick answer

Subtraction is when you take away or find out what is left. In a sailing maths quest, you might start with 10 treasure chests and lose 3 on a stormy sea, so you have 7 left. Subtraction helps you work out how many things are left after some are taken away.

Learning outcome

By the end of this page, you will be able to subtract numbers up to 20 using objects, drawings, and real-life situations, like planning a sailing trip or counting your treasure. Success signs:
  • You can take away objects and count how many are left
  • You can draw pictures to show subtraction
  • You can solve story problems about sailing or treasure
  • You can use a number line to count backwards

Why this matters

Subtraction helps you solve problems in real life, like:
  • How many cookies are left after sharing with friends?
  • How many miles are left to sail to your island?
  • How many pirates are left after some are captured?
In sailing, you might start with 15 bottles of water, but 4 get lost in a storm. You need to subtract to find out how many bottles are left. This helps you plan and make smart choices on your adventure.

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 do it step by step:
  1. Start with a number (the bigger number)
  2. Take away a smaller number (the one you're subtracting)
  3. Count or calculate what is left
You can subtract using:
  • Counting backwards
  • Using your fingers
  • Counting objects
  • Using a number line

Examples you can see

Let’s imagine you are on a sailing quest:
  • You start with 12 fish in your net
  • You catch 5 more fish
  • Then you give 3 fish to your friend
  • How many fish do you have left?
First, you add 12 + 5 = 17 fish. Then, you subtract 17 − 3 = 14 fish. So you have 14 fish left. Another example:
  • You have 10 treasure maps
  • You lose 3 maps in a storm
  • How many maps do you have now?
You start with 10 maps. You take away 3 maps. 10 − 3 = 7 maps. So you have 7 maps left.

Try it as a mini adventure

Adventure: The Sailing Quest You are captain of a ship and have 15 coins in your treasure chest. Your ship sails to a port and you trade 6 coins for new supplies. Then, you find a hidden cave and lose 2 coins while exploring. How many coins do you have left?
  1. Start with: 15 coins
  2. After trade: 15 − 6 = ? coins
  3. After cave: ? − 2 = ? coins
Answer: 15 − 6 = 9 coins 9 − 2 = 7 coins You have 7 coins left. Mini challenge: Draw a picture of your ship with 10 fish in the net. Then, cross out 4 fish because they escaped. How many fish are left?

Common mistakes

  • Mistake: Thinking 8 − 5 = 13 instead of 3. Why it happens: Confusing addition with subtraction. Fix: Use objects or a number line to count backwards.
  • Mistake: Starting with the smaller number and subtracting the bigger one. Why it happens: Not understanding the order of subtraction. Fix: Always start with the bigger number when subtracting.
  • Mistake: Forgetting to count backwards. Why it happens: Thinking subtraction is like adding. Fix: Use a number line or count backwards on fingers.

Parent and carer guide

As a parent or carer, you can help your child by:
  • Using real-life examples like sharing food or counting toys
  • Playing subtraction games using everyday objects
  • Encouraging your child to draw pictures to show subtraction
  • Using number lines to help count backwards
  • Practising with simple subtraction sentences like 10 − 3 = 7
Try asking questions like:
  • “If you had 8 sweets and ate 3, how many are left?”
  • “Can you show me how you counted backwards?”
  • “What does the minus sign mean?”
Remember to be patient and celebrate small successes. Subtraction takes practice, but it becomes easier with time.

Practice questions

  1. There are 12 shells on the beach. You take 5 shells home. How many shells are left?
  2. You have 15 stars in your drawing. You erase 6 stars. How many stars are left?
  3. There are 9 balloons. 4 balloons pop. How many balloons are left?
  4. You have 14 seashells. You give 7 to your friend. How many seashells do you have now?
  5. There are 11 pirates on the ship. 3 go to find treasure. How many pirates are left on the ship?
Answers:
  1. 12 − 5 = 7 shells
  2. 15 − 6 = 9 stars
  3. 9 − 4 = 5 balloons
  4. 14 − 7 = 7 seashells
  5. 11 − 3 = 8 pirates

FAQ

What is subtraction?

Subtraction is taking away or finding what is left. It uses the minus sign (−) and the equals sign (=).

How can I practice subtraction at home?

You can use objects like toys, fruits, or coins. Try taking some away and counting what is left.

Why do we use subtraction in sailing?

Subtraction helps you work out how many things you have left after some are lost, used, or given away.

Can I use a number line for subtraction?

Yes! You can count backwards on a number line to subtract numbers.

What are some real-life examples of subtraction?

Examples include sharing food, counting how many toys are left, or working out how many miles are left to travel.