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Maths Adventures

Ocean maths quest: subtraction

A story-led junior maths adventure using reefs, ships and underwater maps to work out what is left after trades, rescues or escapes.

Quick answer

Subtraction is taking away or finding what is 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 understand how to use subtraction to find what is left when some things are taken away, and you will be able to solve simple subtraction problems using objects, pictures, and numbers. Success signs:
  • You can take away objects and count how many are left
  • You can draw pictures to show subtraction
  • You can write simple subtraction sentences like 5 - 2 = 3
  • You can solve word problems about taking things away

Why this matters

Subtraction helps you understand how much is left when things are taken away. It's useful when you're sharing toys, counting your pocket money, or even when you're on an ocean adventure! Whether you're a pirate captain, a scientist studying ocean life, or just helping at home, subtraction helps you work out what's left after something is taken away.

How it works

Subtraction is like taking away. You start with a group of things, take some away, and then count how many are left. Let's think of it like this:
  1. Start with some objects or numbers
  2. Take some away (subtract them)
  3. Count what is left
For example, if you have 8 fish and 3 swim away, you take away 3 from 8. You count how many are left: 5 fish.

Examples you can see

Here are some fun examples of subtraction in action: Example 1: Fish in the Reef Imagine you have 6 clownfish in a coral reef. 2 swim away to explore the ocean. How many are left?
  • Start with: 6 fish
  • Take away: 2 fish
  • Count what's left: 4 fish
So 6 - 2 = 4 Example 2: Treasure Chest A pirate has 9 gold coins in his treasure chest. He gives 4 coins to his shipmate. How many coins are left?
  • Start with: 9 coins
  • Take away: 4 coins
  • Count what's left: 5 coins
So 9 - 4 = 5 Example 3: Underwater Rescue A marine rescue team has 10 life jackets. 5 are given to people in trouble. How many life jackets are left?
  • Start with: 10 life jackets
  • Take away: 5 life jackets
  • Count what's left: 5 life jackets
So 10 - 5 = 5

Try it as a mini adventure

Adventure: Ocean Rescue Mission You are a young ocean explorer on a mission to save sea creatures. Here's your quest: 1st time: You start with 12 sea turtles on a beach. 3 are safely moved to a rescue center. How many are left? 2nd time: 5 more turtles are found floating in the water. How many are there now? 3rd time: 4 turtles are taken to a rehabilitation centre. How many are left? 4th time: You find 6 baby sea turtles in a nest. 2 are returned to the sea. How many are left? What are the answers to each step? Answers: 1st time: 12 - 3 = 9 turtles 2nd time: 9 + 5 = 14 turtles 3rd time: 14 - 4 = 10 turtles 4th time: 6 - 2 = 4 turtles

Common mistakes

  • Mistake: Confusing which number to start with and which to take away.
    Why it happens: Children might get mixed up when reading a word problem.
    Fix: Always look for key words like "take away", "left", "away", "lost", "gave". The first number is what you start with, the second is what you take away.
  • Mistake: Thinking subtraction means adding.
    Why it happens: Some children mix up addition and subtraction.
    Fix: Remember: subtraction means "take away", so you always get fewer. Addition means "put together", so you get more.
  • Mistake: Not counting backwards properly.
    Why it happens: When counting backwards, it's easy to skip numbers.
    Fix: Use your fingers or draw dots to count backwards. For example, for 7 - 3, count backwards 3 steps from 7: 7, 6, 5, 4. So 7 - 3 = 4.

Parent and carer guide

You can help your child practice subtraction with everyday activities:
  • Count objects together and take some away, then count what's left
  • Use food items like grapes or cookies to show subtraction
  • Play subtraction games with cards or dice
  • Read word problems together and act them out
  • Ask questions like "If you had 8 crayons and lost 3, how many are left?"
Remember, it's okay if your child makes mistakes. Subtraction takes practice. Encourage them to use their fingers, draw pictures, or use real objects to help them think.

Practice questions

  1. There are 7 seashells on the beach. 3 are picked up. How many are left?
  2. A ship has 10 flags. 4 flags are taken down. How many flags are left?
  3. There are 15 jellyfish in the water. 6 swim away. How many are left?
  4. There are 8 dolphins in the ocean. 2 jump out of the water. How many are left?
  5. There are 12 starfish on the seabed. 5 are collected. How many are left?
Answers: 1. 7 - 3 = 4 2. 10 - 4 = 6 3. 15 - 6 = 9 4. 8 - 2 = 6 5. 12 - 5 = 7

FAQ

What is subtraction?

Subtraction is when you take something away from a group. It helps you find out how many are left.

How can I practice subtraction at home?

You can use everyday objects like toys, fruit, or crayons. Try taking some away and counting what's left. You can also draw pictures or use number lines.

What's the opposite of subtraction?

The opposite of subtraction is addition. When you add, you put things together to make more. When you subtract, you take things away to make fewer.

Why do we need to learn subtraction?

Subtraction helps us in many situations, like sharing toys, counting money, or knowing how many cookies are left after eating some. It's useful in school, at home, and when you're out exploring!

What if I don't know the answer to a subtraction problem?

That's okay! You can use your fingers, draw pictures, count backwards, or use objects to help you. The more you practice, the easier it gets!