Mermaid maths quest: subtraction

Quick answer

Subtraction is about finding out what is left when you take something away. In a Mermaid maths quest, you might start with 10 pearls and give 3 away, leaving 7 pearls behind.

Learning outcome

By the end of this page, you will understand how to use subtraction to find what is left after taking something away, and you'll be able to solve simple subtraction problems using pictures, objects, and numbers.

• You can show subtraction with objects or drawings
• You can solve simple subtraction problems using number lines
• You can use subtraction to solve problems about giving away or losing things
• You can explain what subtraction means in everyday situations

Why this matters

Subtraction helps you work out how many things are left when you give some away, lose some, or use some. In the underwater world of a Mermaid maths quest, you might need to know how many shells you have left after trading some, or how many fish are left after helping a friend. Subtraction is used in many parts of life – like when you share your snacks, count how many toys you have, or work out how much money you have left after buying something.

How it works

Subtraction is the opposite of addition. When you add, you put things together. When you subtract, you take things away. The symbol for subtraction is − (minus). For example, if you have 5 shells and give 2 away, you can write this as: 5 − 2 = 3.

1. Start with a number of things (like 5 shells)
2. Take away some of those things (like 2 shells)
3. Count how many are left (like 3 shells)

Examples you can see

Imagine you are a mermaid collecting shells. You find 8 shells on the seafloor. Then, you give 3 shells to your friend. How many shells do you have left?

• You start with 8 shells
• You give away 3 shells
• You count the shells left: 8 − 3 = 5 shells

Another example: You have 12 pearls. You give 5 to help a sea turtle get out of a net. How many pearls do you have now?

• You start with 12 pearls
• You give away 5 pearls
• You count the pearls left: 12 − 5 = 7 pearls

Here is a subtraction table showing how many shells you have left if you start with 10 shells and give away different numbers:

Try it as a mini adventure

Join a Mermaid maths quest! You are on a treasure hunt underwater. You start with 15 seashells. Along the way, you meet a baby whale who needs help. You give the baby whale 6 shells to make its swim easier. Then, you find a hidden cave and collect 4 more shells. How many shells do you have now?

1. Start with 15 shells
2. Give away 6 shells: 15 − 6 = 9 shells
3. Find 4 more shells: 9 + 4 = 13 shells

But wait! You also need to give 3 shells to a friendly octopus who is lost. How many shells do you have now?

1. Start with 13 shells
2. Give away 3 shells: 13 − 3 = 10 shells

You have 10 shells left for your final treasure chest!

Common mistakes

• Mistake: Thinking that 8 − 3 = 5, but confusing it with 8 + 3 = 11.
• Why it happens: Mixing up addition and subtraction symbols.
• Fix: Use objects or drawings to help you see what subtraction means.

• Mistake: Subtracting a larger number from a smaller number (like 3 − 5).
• Why it happens: Not yet understanding that subtraction shows how much is left.
• Fix: For now, only subtract smaller numbers from bigger numbers. Later, you'll learn about negative numbers.

• Mistake: Forgetting to count how many are left after taking some away.
• Why it happens: Rushing through the problem or not using objects.
• Fix: Count your objects carefully or draw them to help you see what's left.

Parent and carer guide

Help your child understand subtraction by using everyday examples. For instance, if you have 10 cookies and eat 3, ask how many are left. You can use real objects like buttons, toys, or pasta to show subtraction. Try this 5-minute activity:

1. Give your child 8 small objects (like coins or blocks)
2. Ask them to give you 2 objects and count how many are left
3. Repeat with different numbers to build confidence
4. Encourage them to draw pictures of their subtraction problems
5. Ask questions like, "How many more do you need to take away to have 0 left?"

Remember: It's okay if they make mistakes. Subtraction takes practice, and every mistake is a learning opportunity.

Practice questions

1. What is 7 − 2?
2. You have 10 sea stars. You give 4 to a friend. How many do you have left?
3. There are 12 pearls. You take 5. How many are left?
4. Start with 9 shells. Give away 6. How many shells are left?
5. What is 15 − 8?

Answers:

1. 5
2. 6
3. 7
4. 3
5. 7

FAQ

What does subtraction mean?

Subtraction means taking something away to find out how much is left. It's like giving some of your toys to a friend and counting how many you still have.

Why do we use subtraction?

We use subtraction to know how many things are left after we give some away, lose some, or use some. It helps us in everyday life, like when sharing snacks or saving money.

How can I practice subtraction at home?

You can practice subtraction by using toys, food, or drawings. Try asking questions like, "If you have 6 candies and eat 2, how many are left?"

What is the opposite of subtraction?

The opposite of subtraction is addition. If you take away 3 shells, you can add 3 shells back to get the same number.

Can I subtract a bigger number from a smaller one?

For now, you can only subtract a smaller number from a bigger number. Later, you will learn about negative numbers, which are smaller than zero.