Decimals — for parents
Decimals are the bridge between fractions (which children met in Year 3) and the more flexible numbers they'll use forever after. In Year 4 the focus is on tenths and hundredths — the structure that makes money, measurement and percentages possible.
What your child should master by year-end
- Read and write decimals with one or two decimal places (3.4, 0.27, 12.05).
- Identify each digit's place value: tenths and hundredths.
- Place a decimal on a 0–1 (or wider) number line.
- Compare two decimals using <, > and =.
- Recognise the link between decimals and fractions of tenths/hundredths.
Common mistakes
"More digits = bigger number"
This is correct for whole numbers (1 000 > 999), but wrong for decimals. 0.65 < 0.7 even though 0.65 looks "longer".
Help: line up the decimal points and add trailing zeros to make the lengths match. 0.65 vs. 0.70. Now 70 > 65 visually.Confusing tenths with tens
The words sound similar but the values are a hundred times apart. The "tens" sit to the left of the decimal point; the "tenths" sit just to the right.
Help: build a place-value table. Show that 1 ten = 10, but 1 tenth = 0.1.Dropping the leading zero
Children sometimes write ".5" instead of "0.5". It's not technically wrong, but it's easy to misread or miss completely.
Help: insist on the leading zero. "We always write zero point five so there's no chance of skipping the point."Trailing zero confusion
Some children think 0.50 is "bigger than" 0.5. They aren't different — they're the same number written with different precision.
Help: practise: "0.5 is five tenths. 0.50 is fifty hundredths. Fifty hundredths is five tenths. Same number."Things to try at home
Money talk
Decimals show up everywhere in money. "How much is £2.45 and £1.30 together?" "If you split £6.50 between 5 people, how much does each get?" Real prices make the abstraction concrete.
Measure the kitchen
Use a tape measure and read lengths to the nearest centimetre. A counter that's 1.45 m long is 1 m and 45 hundredths of a metre. Connect the decimal to the fraction.
Number-line drawing
Draw a long line from 0 to 1 on a piece of paper. Together, mark every tenth (0.1, 0.2, …, 0.9). Then pick a few decimals — 0.3, 0.65, 0.07 — and ask your child to point to where they go.
Understanding the place value
A decimal works on the same "tens times bigger" rule as whole numbers, just running the other way past the point: every place to the right is ten times smaller.
| 100 | 10 | 1 | . | 0.1 | 0.01 |
If your child masters that one idea — each step right is ten times smaller — every rule about decimals (comparing, ordering, adding) follows naturally.