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decimals

Tenths as decimals

Connect 1/10 to 0.1 using grids, money and measures.

Quick answer

One-tenth (1/10) as a decimal is written as 0.1. This means that if you divide something into 10 equal parts, one part is 0.1 of the whole.

Learning outcome

By the end of this page, you will understand how to show one-tenth as a decimal (0.1) and use this knowledge to solve simple problems with money, measures, and shapes. Success signs:
  • You can draw a grid and shade one-tenth of it
  • You can match 1/10 to 0.1 in different contexts
  • You can use 0.1 to count money or measure small amounts
  • You can explain that 0.1 means one part out of ten equal parts

Why this matters

Understanding tenths as decimals is important because it helps you work with money, time, and measurements in everyday life. You'll use this knowledge when:
  • Counting coins (like 10p pieces)
  • Measuring things (like 0.1 of a metre)
  • Sharing food equally
  • Playing games that involve scoring or timing

How it works

Decimal numbers use a point (called a decimal point) to separate whole numbers from parts. The first digit after the decimal point shows how many tenths there are.
  1. Think of a whole object, like a cake or a square
  2. Split it into 10 equal parts
  3. One part is 1/10 or 0.1
  4. Two parts are 2/10 or 0.2
  5. And so on, up to 10/10 which equals 1 whole

Examples you can see

Let's imagine you have a big chocolate bar that you want to share equally with 9 friends. That means you split it into 10 equal pieces. Each piece is one-tenth (1/10) of the whole bar.
  • One piece = 1/10 = 0.1 of the bar
  • Two pieces = 2/10 = 0.2 of the bar
  • Five pieces = 5/10 = 0.5 of the bar
Using grids to show tenths: Grid showing tenths
Whole square1/102/103/10
100%10%20%30%
1.00.10.20.3
Using money:
  • 10p piece = 1/10 of £1 = 0.1 of £1
  • Two 10p pieces = 2/10 of £1 = 0.2 of £1
  • Five 10p pieces = 5/10 of £1 = 0.5 of £1
Using measures:
  • 10cm = 1/10 of 1 metre = 0.1m
  • 20cm = 2/10 of 1 metre = 0.2m
  • 50cm = 5/10 of 1 metre = 0.5m

Try it as a mini adventure

Adventure: The Decimal Detective You are a detective trying to solve a mystery. A treasure map shows that the treasure is hidden 0.1 of the way along a path. You have to walk 10 steps to reach the end of the path.
  1. 1st time: Walk 0.1 of the path = 1 step
  2. 2nd time: Walk 0.2 of the path = 2 steps
  3. 3rd time: Walk 0.3 of the path = 3 steps
  4. 4th time: Walk 0.4 of the path = 4 steps
  5. 5th time: Walk 0.5 of the path = 5 steps
  6. 6th time: Walk 0.6 of the path = 6 steps
  7. 7th time: Walk 0.7 of the path = 7 steps
  8. 8th time: Walk 0.8 of the path = 8 steps
  9. 9th time: Walk 0.9 of the path = 9 steps
  10. 10th time: Walk 1.0 of the path = 10 steps (treasure found!)

Common mistakes

  • Mistake: Thinking 0.1 means 10 whole items instead of 1 out of 10 parts.
    Why it happens: Confusing the decimal point with a regular number.
    Fix: Remember that 0.1 is smaller than 1 whole. It's like having one piece from a cake cut into ten pieces.
  • Mistake: Writing 0.01 instead of 0.1 for one-tenth.
    Why it happens: Getting confused about which digit goes where after the decimal point.
    Fix: One-tenth is 0.1, two-tenths is 0.2, and so on. The first digit after the point is always the number of tenths.
  • Mistake: Mixing up tenths and hundredths.
    Why it happens: Both are decimal places, so they look similar.
    Fix: Remember that 0.1 = 1/10, and 0.01 = 1/100. The second digit after the decimal point is always the number of hundredths.

Parent and carer guide

To help your child learn about tenths as decimals:
  • Use everyday objects like coins, rulers, or chocolate bars to show how things can be split into 10 equal parts
  • Practice counting in tenths: "0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0"
  • Ask your child to find 0.1 of different amounts, like 0.1 of 10 apples or 0.1 of 100cm
  • Play games where you count steps or measure things using tenths
  • Remember: It's okay if your child makes mistakes - they're learning!

Practice questions

  1. What is 1/10 written as a decimal?
  2. Which is bigger: 0.3 or 0.7?
  3. How much is 0.5 of 100cm?
  4. What is 3/10 written as a decimal?
  5. Which decimal shows 8 tenths?
Answers:
  1. 0.1
  2. 0.7
  3. 50cm
  4. 0.3
  5. 0.8

FAQ

What does 0.1 mean in maths?

0.1 means one part out of ten equal parts. It's the same as 1/10.

How do I know if I have one-tenth of something?

If you split something into 10 equal parts and take one part, you have one-tenth (0.1).

Can I write 0.1 as a fraction?

Yes! 0.1 is the same as 1/10.

Why is 0.1 smaller than 1?

Because 0.1 means 1 part out of 10 parts, which is less than the whole thing.

How do I use tenths in real life?

You use tenths when counting money (like 10p pieces), measuring things (like 10cm), or sharing food (like taking one slice from ten slices).