Pirate maths quest: decimals

Quick answer

You can use decimals to measure small parts of things, like distances, money, or scores, using tenths and hundredths. A decimal number like 0.7 means 7 parts out of 10, and 0.25 means 25 parts out of 100.

Learning outcome

By the end of this page, you will be able to understand and use decimals to show small parts of a whole, like 0.5 for half or 0.25 for a quarter, in real-life situations like measuring distance, counting money, or scoring points.

• You can show 0.5 as half a pizza
• You can understand that 0.25 is a quarter of something
• You can use decimals to measure small amounts of money or distance
• You can compare decimals like 0.3 and 0.7 to see which is bigger

Why this matters

Decimals help you understand small parts of things in the real world. When you're shopping and see prices like £2.99, or when you're on a treasure hunt and need to measure 0.5 metres, decimals help you count and compare parts of whole things. They're used in cooking, games, science, and money. Understanding decimals is like having a superpower to measure and share small amounts!

How it works

Decimals are numbers that have a dot in them, like 0.3 or 1.75. The dot is called a decimal point. Everything to the left of the decimal point is a whole number, and everything to the right shows parts of a whole.

1. Think of a whole pizza. If you cut it into 10 equal slices, each slice is 0.1 (one-tenth) of the pizza.
2. If you take 3 slices, you have 0.3 (three-tenths) of the pizza.
3. If you cut the pizza into 100 slices, each slice is 0.01 (one-hundredth) of the pizza.
4. So, 25 slices would be 0.25 (twenty-five-hundredths) of the pizza.

Examples you can see

Here are some ways you might see decimals in real life:

Example 1: Pirate Treasure Map

On your pirate treasure map, the distance to the treasure is 2.5 metres. This means 2 whole metres and 5 tenths of a metre (or 50 centimetres). You can think of it like 2 full steps and half a step.

Example 2: Pirate Coins

You find some coins: 1.25 pounds. This means 1 whole pound and 25 hundredths of a pound. If you had 25 one-penny coins, that would be 0.25 pounds.

Example 3: Pirate Score

In your pirate game, you score 0.8 points for each treasure you find. If you find 5 treasures, you score 0.8 + 0.8 + 0.8 + 0.8 + 0.8 = 4 points.

Example 4: Pirate Supplies

Your ship needs 0.75 litres of water per person. If there are 4 pirates, you need 0.75 × 4 = 3 litres of water.

Try it as a mini adventure

Imagine you're a pirate captain on a treasure hunt. Your ship has 4 crew members, and you need to divide 3.2 litres of water equally among them.

1. First, you need to know how much water each pirate gets.
2. You can split 3.2 litres by 4 people.
3. Each pirate gets 0.8 litres of water.
4. But wait! You also need to share 0.6 kilograms of food equally among 4 people.
5. Each pirate gets 0.15 kilograms of food.

Now you know how much water and food each pirate gets. You're a great pirate captain!

Common mistakes

• Mistake: Thinking 0.5 is bigger than 0.75 because 5 is bigger than 7.
• Why it happens: Children often compare the digits without understanding the decimal place value.
• Fix: Remember that 0.75 means 75 parts out of 100, which is more than 0.5 (50 parts out of 100).

• Mistake: Adding decimals like 0.3 + 0.2 = 0.53.
• Why it happens: Children may add the numbers in the tenths place and the hundredths place separately, like 3 + 2 = 5 and then put 3 at the end.
• Fix: Align the decimal points and add as 0.3 + 0.2 = 0.5.

• Mistake: Writing 0.5 as 0.50 or 0.500.
• Why it happens: Children might think adding zeros makes the number bigger.
• Fix: 0.5, 0.50, and 0.500 are all the same value – they're just written differently.

Parent and carer guide

Helping your child with decimals doesn’t need to be hard. Here are some tips:

• Use real-life examples like shopping or cooking to show how decimals are used.
• Play games with money, like counting coins and seeing how much 0.25 or 0.50 pounds is.
• Draw pictures of pizzas or cakes divided into tenths or hundredths to show decimal parts.
• Don’t worry if they make mistakes – that’s part of learning!
• Practice by asking questions like, “If we split 0.8 of a pizza between 2 people, how much does each person get?”

Practice questions

1. What is 0.4 of a pizza?
2. How much is 0.25 in terms of a quarter?
3. Which is bigger: 0.6 or 0.35?
4. What is 0.3 + 0.2?
5. How much is 0.75 × 2?

Answers:

1. 0.4 is 4 parts out of 10, so 4 slices if the pizza is cut into 10 slices.
2. 0.25 is a quarter, or 25 parts out of 100.
3. 0.6 is bigger because 6 tenths is more than 3 tenths and 5 hundredths.
4. 0.3 + 0.2 = 0.5
5. 0.75 × 2 = 1.5

FAQ

What is a decimal?

A decimal is a number that has a dot in it, like 0.5 or 1.25. The dot separates whole numbers from parts of a whole.

How do I know which decimal is bigger?

Compare the digits from left to right. If the whole number parts are the same, look at the tenths place, then the hundredths place.

Why do we use decimals?

Decimals help us measure small parts of things, like money, distances, or amounts of ingredients. They make it easier to be precise.

Can I add decimals like regular numbers?

Yes! But always line up the decimal points. For example, 0.4 + 0.3 = 0.7.

What does 0.1 mean?

0.1 means 1 part out of 10, or one-tenth. If you split a whole into 10 parts, 0.1 is one of those parts.