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Maths Adventures

Volcano maths quest: subtraction

A story-led junior maths adventure using lava paths, safety zones and eruption data to work out what is left after trades, rescues or escapes.

Quick answer

Subtraction is about finding what is left when you take something away. In the Volcano Maths Quest, you'll use subtraction to work out how many lava flows are left, how many people are rescued, or how much time is left before an eruption.

Learning outcome

By the end of this page, you will be able to solve subtraction problems using objects, pictures, and numbers when something is taken away from a group or amount. Success signs:
  • You can find the difference between two numbers
  • You can use subtraction to solve problems about taking away
  • You can show subtraction using pictures or counters
  • You can solve real-life subtraction problems

Why this matters

Subtraction helps you understand how much is left when you give something away, lose something, or use some of your resources. In the volcano quest, you'll need to subtract to find out how many lava flows are still coming, how many people are still in danger, or how much time is left before the next eruption. Subtraction is used in everyday life too – like when you share your snacks, pay for things, or count down the minutes until your favourite TV show starts.

How it works

Subtraction means taking something away from a group or amount. You can think of it like this:
  1. Start with a number or group (this is called the "minuend")
  2. Take away some of it (this is called the "subtrahend")
  3. Count how much is left (this is called the "difference")
You can show subtraction with:
  • Counters or objects
  • Drawings or pictures
  • Number lines
  • Number sentences (like 8 - 3 = 5)

Examples you can see

Let’s imagine you are on a volcano adventure. Here are some real examples of subtraction in action: Example 1: Counting lava flows You see 10 lava flows coming down the mountain. 3 of them have already reached the valley. How many lava flows are still coming?
  • Start with 10 lava flows
  • Take away 3 lava flows
  • Count how many are left: 10 - 3 = 7
Example 2: Rescuing people There are 12 people trapped in the lava zone. 5 people have already been rescued. How many people are still in danger?
  • Start with 12 people
  • Take away 5 people
  • Count how many are left: 12 - 5 = 7
Example 3: Time before eruption The volcano is about to erupt in 15 minutes. If 6 minutes have already passed, how much time is left?
  • Start with 15 minutes
  • Take away 6 minutes
  • Count how many are left: 15 - 6 = 9

Try it as a mini adventure

The Volcano Rescue Mission You are part of a team trying to save people from a volcano that is about to erupt. Your mission is to work out how many people are still in danger and how much time is left. Step 1: There are 20 people in the danger zone. 7 people have already been rescued.
  • How many people are still in danger? 20 - 7 = ?
Step 2: The eruption is due in 18 minutes. 4 minutes have already passed.
  • How much time is left before the eruption? 18 - 4 = ?
Step 3: The lava flows are coming down at a rate of 15 per hour. 6 lava flows have already reached the valley.
  • How many lava flows are still coming? 15 - 6 = ?
Step 4: The rescue team has 10 emergency kits. 3 have already been used.
  • How many emergency kits are left? 10 - 3 = ?
Step 5: The volcano is 12 km from the nearest town. 5 km of the path has been cleared.
  • How much distance is still blocked? 12 - 5 = ?

Common mistakes

  • Mistake: Thinking that 8 - 3 = 11 instead of 5.
    Why it happens: Confusing subtraction with addition.
    Fix: Use counters or draw pictures to show the difference clearly.
  • Mistake: Forgetting to start with the bigger number.
    Why it happens: Not understanding that subtraction finds what is left.
    Fix: Always check that the number you start with is larger than the one you take away.
  • Mistake: Subtracting in the wrong order.
    Why it happens: Rushing or not reading the problem carefully.
    Fix: Read the problem twice and write down the numbers clearly.

Parent and carer guide

Subtraction is a key part of early maths. Parents can help by:
  • Using everyday situations to practice subtraction (like sharing snacks or counting toys)
  • Encouraging children to draw pictures or use objects to show their thinking
  • Reading subtraction problems aloud and asking the child to explain what they are doing
  • Using number lines or counters to make subtraction visual
  • Being patient and praising effort, not just correct answers
Subtraction is not just about numbers – it’s about understanding what happens when something is taken away. Keep the focus on the story and the real-world problems, not just the maths.

Practice questions

  1. There are 12 lava flows. 5 have already passed. How many are left? Answer: 7
  2. There are 15 people in the danger zone. 8 have been rescued. How many are still in danger? Answer: 7
  3. There are 20 emergency kits. 6 have been used. How many are left? Answer: 14
  4. There are 18 minutes until eruption. 9 minutes have passed. How many minutes are left? Answer: 9
  5. There are 10 people in the cave. 3 have escaped. How many are still inside? Answer: 7
  6. There are 14 lava flows coming. 4 have reached the valley. How many are still coming? Answer: 10
  7. There are 16 rescue teams. 7 have been sent. How many are still waiting? Answer: 9
  8. There are 13 km to the safe zone. 5 km have been cleared. How much is still blocked? Answer: 8
  9. There are 11 people trapped. 4 have been rescued. How many are still trapped? Answer: 7
  10. There are 17 emergency supplies. 9 have been used. How many are left? Answer: 8

FAQ

What is subtraction?

Subtraction is the maths operation where you take something away from a group or amount to find out how much is left.

How do I know when to use subtraction?

You use subtraction when something is taken away, lost, or used up. For example, if you have 10 apples and eat 3, you subtract to find out how many are left.

Can I use subtraction with big numbers?

Yes! Subtraction works with any numbers – small or big. You can subtract 2 from 200 or 15 from 1000.

How can I practice subtraction at home?

You can practice by counting toys, sharing snacks, or using a number line. Try asking questions like: "If I have 12 crayons and give 5 to my friend, how many do I have left?"

What are some fun ways to learn subtraction?

Try drawing pictures, using counters, playing subtraction games, or solving puzzles. You can also pretend to be a volcano rescuer and solve subtraction problems in your head!