Age 9 guide to decimals

Quick answer

Decimals are a way to write parts of a whole number, like 0.5 which means half, or 0.25 which means a quarter. At age 9, you'll learn to read, write, compare, and add decimals up to two decimal places.

Learning outcome

By the end of this page, you will be able to:

• Read and write decimals to two decimal places
• Compare decimals using the correct symbols (<, >, =)
• Add decimals that are less than 1
• Understand how decimals relate to money and measurements

Why this matters

Decimals help you understand parts of things more clearly. You use decimals when you share a pizza, measure ingredients for baking, or count money. They're important for understanding how much things cost, how far you've walked, or how tall you are. Decimals are used in science, cooking, shopping, and even video games!

How it works

Decimals are numbers that have a decimal point (.) and show parts of a whole. Think of a whole pizza. If you eat half of it, you've eaten 0.5 of the pizza. If you eat one-quarter, that's 0.25 of the pizza. The decimal point separates the whole number from the part.

Let's break it down:

1. Whole numbers are to the left of the decimal point
2. The first digit to the right of the decimal point is the tenths place
3. The second digit to the right of the decimal point is the hundredths place

For example, in 0.63:

• 0 is the whole number (no whole pieces)
• 6 is in the tenths place (6 tenths)
• 3 is in the hundredths place (3 hundredths)

Examples you can see

Let's imagine you're at a sweet shop. You want to buy some sweets that cost 0.75 pounds each.

Reading decimals:

• 0.5 means 5 tenths, or half
• 0.25 means 25 hundredths, or a quarter
• 0.8 means 8 tenths, or 80 hundredths

Comparing decimals:

Which is more: 0.4 or 0.6?

0.6 is bigger because 6 tenths is more than 4 tenths.

Adding decimals:

Imagine you have 0.3 of a cake and your friend gives you 0.5 of a cake:

0.3 + 0.5 = 0.8

That's 8 tenths of a cake!

Try it as a mini adventure

Adventure: The Decimal Bakery

You're a baker at a special bakery that only sells items in decimal amounts. Your mission is to make sure all your cakes, cookies, and biscuits are priced correctly using decimals.

4th time: You have 0.4 of a cake left. You sell 0.1 of a cake. How much do you have left?

5th time: You have 0.7 of a cookie. You eat 0.3 of a cookie. How much do you have left?

6th time: You have 0.2 of a biscuit. Your friend gives you 0.5 of a biscuit. How much do you have now?

7th time: You have 0.9 of a muffin. You give 0.4 of a muffin to your helper. How much do you have left?

8th time: You have 0.6 of a pie. You eat 0.2 of a pie. How much do you have left?

Common mistakes

• Mistake: Thinking 0.4 is bigger than 0.6 because 4 is bigger than 6
• Why it happens: Children often compare the numbers after the decimal point without understanding place value
• Fix: Remember that 0.4 means 4 tenths and 0.6 means 6 tenths. The larger number of tenths is bigger

• Mistake: Adding 0.3 + 0.2 = 0.53
• Why it happens: Confusing how to add decimals with how to write them
• Fix: Add the tenths together (3 + 2 = 5) and write 0.5, not 0.53

• Mistake: Writing 0.12 as 0.1 and 0.2
• Why it happens: Not understanding that 0.12 means 12 hundredths, not 1 tenth and 2 tenths
• Fix: Remember the place values: tenths, hundredths, thousandths

Parent and carer guide

Help your child understand decimals by:

1. Using real money to show how 0.50 pounds is the same as 50 pence
2. Measuring ingredients when cooking together
3. Playing games with decimal cards or dice
4. Practicing with everyday items like rulers, scales, or clocks
5. Reinforcing that decimals are just another way to show parts of a whole

Watch for confusion between place values. If your child writes 0.7 as 0.70, that's okay – they're thinking about it! Just make sure they understand that 0.7 and 0.70 are the same amount.

Keep practice fun and short. Ten minutes of daily practice is better than one long session. Celebrate progress, not just perfect answers.

Practice questions

1. Write 0.75 as a fraction
2. Compare: 0.4 and 0.6. Which is bigger?
3. Add: 0.3 + 0.5
4. What is 0.8 - 0.3?
5. Which decimal is the smallest: 0.1, 0.01, 0.11?

Answers:

1. 0.75 = 75/100 or 3/4
2. 0.6 is bigger
3. 0.8
4. 0.5
5. 0.01 is smallest

FAQ

What does the decimal point mean?

The decimal point separates whole numbers from parts of a whole. Everything to the left is a whole number, and everything to the right shows parts.

How do decimals relate to money?

Money is a great way to understand decimals. £1.50 means 1 pound and 50 pence, or 1 pound plus 5 tenths and 0 hundredths of a pound.

Can I add decimals like regular numbers?

You can add decimals, but you must line up the decimal points. It's like lining up the tenths and hundredths places.

Why are decimals important?

Decimals help us measure things more precisely, like how tall you are, how much water you drink, or how much you weigh. They're used everywhere in science, cooking, and shopping.

How can I practice decimals at home?

Practice with shopping receipts, cooking recipes, measuring tools, or even with coins and banknotes. The more you use decimals in real life, the easier they become.