X Tables
Maths Adventures

Submarine maths quest: addition

A story-led junior maths adventure using depths, pressure and hidden coordinates to combine treasures, supplies and scores without losing track.

Quick answer

By the end of this page, you will be able to add numbers together to find totals in fun submarine adventures!

Learning outcome

By the end of this page, you will be able to add numbers together to find totals when exploring the deep sea, using treasures, supplies, and scores. Success signs:
  • You can add two small numbers together (like 3 + 4 = 7)
  • You can add larger numbers together (like 12 + 15 = 27)
  • You can solve problems about your submarine's supplies and treasures
  • You can use addition to keep track of your underwater score

Why this matters

Addition is like putting things together to see how many you have altogether. When you're exploring the deep sea, you need to add up your treasures, supplies, and points to know how well you're doing. This helps you make good decisions, like whether you have enough food for your journey or how many coins you've collected. Addition is used everywhere – in games, cooking, shopping, and even in space missions!

How it works

Addition is when we put things together. Let's imagine you're on a submarine and you find treasures:
  • First, you find 5 shiny coins
  • Then, you find 3 more coins
  • Now, you add them together: 5 + 3 = 8 coins
We can also add bigger numbers:
  • You have 12 fish in your tank
  • Your friend gives you 7 more fish
  • Now you have: 12 + 7 = 19 fish

Examples you can see

Let's go on a submarine adventure! Here are some examples of addition you might find underwater: Example 1: Treasures You find 6 gold bars and then find 4 more gold bars.
  • 6 + 4 = 10 gold bars
Example 2: Supplies Your submarine has 8 bottles of oxygen and you get 5 more.
  • 8 + 5 = 13 bottles of oxygen
Example 3: Score In your underwater game, you score 15 points and then 9 more points.
  • 15 + 9 = 24 points
Example 4: Depth You dive down 10 metres and then go 7 more metres deeper.
  • 10 + 7 = 17 metres deep
Example 5: Time Your submarine journey takes 20 minutes and then 15 more minutes.
  • 20 + 15 = 35 minutes total

Try it as a mini adventure

Submarine Treasure Hunt! You are on a submarine exploring the ocean floor. You have a treasure map and need to collect your supplies and coins. 1st time: You find 3 red coins 2nd time: You find 5 blue coins 3rd time: You find 2 green coins 4th time: You find 4 yellow coins 5th time: You find 1 purple coin How many coins have you found?
  • 3 + 5 = 8 coins
  • 8 + 2 = 10 coins
  • 10 + 4 = 14 coins
  • 14 + 1 = 15 coins
Great job! You found 15 coins! Now, let's add your supplies:
  • You have 4 bottles of water
  • You find 3 more bottles
  • How many bottles do you have now?
Answer: 4 + 3 = 7 bottles

Common mistakes

  • Mistake: Forgetting to carry numbers when adding bigger numbers Why it happens: When adding 17 + 8, children might forget to carry the 1 from 15 to the tens column Fix: Use your fingers or draw lines to help you remember to carry the extra number
  • Mistake: Adding the same numbers twice Why it happens: When you have 6 + 6, children might think it's 12 but sometimes get confused Fix: Count on your fingers or use objects to make sure you're adding correctly
  • Mistake: Not lining up numbers correctly Why it happens: When adding 23 + 15, children might put 3 and 5 under each other but forget to align the tens Fix: Write numbers in neat columns with tens under tens and units under units
  • Mistake: Thinking that 1 + 1 = 2, but 1 + 2 = 3, so 2 + 2 = 4, but 2 + 3 = 5, and so on Why it happens: Confusion with the pattern of adding numbers Fix: Practice with simple counting, use number lines, or play addition games

Parent and carer guide

Here's how to help your child with addition:
  • Use everyday situations like counting toys, snacks, or steps to make addition real
  • Ask your child to add up the number of fruits in their lunch box
  • Play addition games with dice or cards
  • Don't worry if your child makes mistakes – they're learning!
  • Encourage your child to show their work with fingers, drawings, or objects
  • Use real-life examples like adding up coins or measuring ingredients for cooking
  • Be patient and celebrate small successes
  • Don't rush – let your child think through problems at their own pace
  • Ask "How did you work that out?" to help them explain their thinking
  • Make it fun with games, stories, or challenges

Practice questions

  1. What is 7 + 8?
  2. What is 12 + 5?
  3. What is 9 + 6?
  4. What is 15 + 4?
  5. What is 11 + 9?
  6. What is 3 + 13?
  7. What is 10 + 10?
  8. What is 14 + 6?
  9. What is 16 + 3?
  10. What is 8 + 12?
Answers:
  1. 7 + 8 = 15
  2. 12 + 5 = 17
  3. 9 + 6 = 15
  4. 15 + 4 = 19
  5. 11 + 9 = 20
  6. 3 + 13 = 16
  7. 10 + 10 = 20
  8. 14 + 6 = 20
  9. 16 + 3 = 19
  10. 8 + 12 = 20

FAQ

What is addition?

Addition is when you put numbers together to find how many you have in total.

How do I add numbers?

You can add numbers by counting on your fingers, using objects, or writing them in columns.

Why do I need to learn addition?

Addition helps you count things, solve problems, and make decisions in everyday life like how much money you have or how many toys you have.

What happens if I add zero?

When you add zero to any number, that number stays the same. For example, 5 + 0 = 5.

How can I practice addition at home?

You can practice by counting your toys, adding up snacks, or playing games with dice or cards.