Maths Adventures
Submarine maths quest: subtraction
A story-led junior maths adventure using depths, pressure and hidden coordinates to work out what is left after trades, rescues or escapes.
Quick answer
Subtraction is like taking away or finding what's left. When you go on a submarine quest, you'll need to subtract to find out how many treasures are left, how much air is left, or how far you've moved.Learning outcome
By the end of this page, you will be able to subtract numbers up to 20 to solve submarine adventure problems, like finding out how many coins are left after trading or how many meters you've descended. Success signs:- You can count back to find the answer to a subtraction problem
- You can solve a word problem about a submarine adventure
- You can use objects or drawings to show subtraction
- You can subtract numbers in your head or with help
Why this matters
Subtraction helps you figure out what's left when you take something away. In a submarine, you might need to know how many coins are left after trading, how much air is left in your tank, or how many meters you've descended. Subtraction is also used when you're sharing food, saving money, or playing games. Understanding subtraction helps you make smart choices and solve problems in your daily life.How it works
Subtraction is about taking away or finding the difference between two numbers. When you subtract, you start with a bigger number and take away a smaller number. The answer is what's left. You can use objects, drawings, or your fingers to help you subtract. Let's use a simple example: If you have 5 fish and you give 2 fish to your friend, how many fish do you have left? You start with 5, take away 2, and you have 3 left. We write this as: 5 - 2 = 3. You can also think of subtraction as "counting back." If you have 7 shells and you give away 3, you count back from 7: 7, 6, 5, 4. So, 7 - 3 = 4.Examples you can see
Here are some submarine-themed examples to help you understand subtraction: Example 1: Coins in the treasure chest You find a treasure chest with 10 coins. You give 4 coins to your submarine buddy. How many coins are left in the chest? We start with 10 coins and take away 4 coins. 10 - 4 = 6 There are 6 coins left in the chest. Example 2: Depth of the ocean Your submarine is at 15 meters below sea level. It dives down 5 more meters. How deep is it now? We start with 15 meters and take away 5 meters. 15 - 5 = 10 The submarine is now 10 meters below sea level. Example 3: Air in the tank You have 12 liters of air in your tank. You use 7 liters for your underwater exploration. How many liters are left? We start with 12 liters and take away 7 liters. 12 - 7 = 5 There are 5 liters of air left in your tank. Example 4: Hidden coordinates Your submarine's computer shows 8 coordinates. You've found 3 of them. How many more coordinates do you need to find? We start with 8 coordinates and take away 3 coordinates. 8 - 3 = 5 You need to find 5 more coordinates.Try it as a mini adventure
Submarine Mission: Find the Lost Treasure You are on a submarine mission to find a lost treasure. You have 12 coins in your treasure bag. You must trade 5 coins for a map to find the treasure. Then, you dive down 4 meters to explore the ocean floor. Finally, you find 3 more coins in a cave. Let's solve this step by step: 1st time: You start with 12 coins. 2nd time: You trade 5 coins for a map. 12 - 5 = 7 coins left. 3rd time: You dive down 4 meters. 4th time: You find 3 more coins. 7 + 3 = 10 coins now. 5th time: You have 10 coins. Mini Challenge: How many coins did you have at the start? How many did you trade? How many did you find? What is the final amount?Common mistakes
- Mistake: Thinking 8 - 3 = 5, but then saying 8 - 3 = 11
Why it happens: Confusing addition with subtraction
Fix: Use counting back or objects to show that 8 - 3 means taking 3 away from 8, which leaves 5 - Mistake: Counting forward instead of backward when subtracting
Why it happens: Not understanding that subtraction means taking away
Fix: Practice counting backwards or use a number line to show subtraction - Mistake: Subtracting a bigger number from a smaller number
Why it happens: Not understanding that subtraction needs a bigger number first
Fix: Remind yourself that you always start with the bigger number in subtraction
Parent and carer guide
Helping your child with subtraction doesn't need to be stressful. Here are 5 simple ways to support your child at home:- Use everyday situations: While shopping, ask "If you had 10 pounds and spent 4 pounds, how much would you have left?"
- Count together: Use fingers, blocks, or coins to show subtraction problems
- Make it fun: Play subtraction games with dice or cards
- Be patient: Let your child solve problems in their own way before showing them a new method
- Encourage mistakes: When your child makes a mistake, ask "How can we check this?" rather than saying "wrong"
Practice questions
- Subtract: 9 - 4 = ?
Answer: 5 - Subtract: 15 - 7 = ?
Answer: 8 - Subtract: 12 - 5 = ?
Answer: 7 - Subtract: 18 - 9 = ?
Answer: 9 - Subtract: 10 - 3 = ?
Answer: 7 - Subtract: 14 - 6 = ?
Answer: 8 - Subtract: 11 - 2 = ?
Answer: 9 - Subtract: 16 - 8 = ?
Answer: 8 - Subtract: 13 - 4 = ?
Answer: 9 - Subtract: 20 - 10 = ?
Answer: 10
FAQ
What is subtraction?
Subtraction is when you take away a number from another number to find out how much is left. It's like sharing or giving away something.
How do I know when to use subtraction?
Use subtraction when something is taken away, shared, or when you want to find the difference between two amounts.
Can I subtract a bigger number from a smaller number?
Yes, but the answer will be a negative number, which is more advanced. For now, we always start with the bigger number.
Why is subtraction important?
Subtraction helps us solve problems in everyday life, like knowing how much change you get from a shop, how many toys are left after sharing, or how far you've moved.
How can I practice subtraction at home?
You can practice by counting backwards, using objects like coins or blocks, playing subtraction games, or solving real-life problems like "If you had 12 cookies and ate 5, how many are left?"