A decimal uses a dot to show parts of a whole. You already use decimals with money, because £3.45 is 3 pounds and 45 pence.
Why this matters: Shop prices, weights and measures all use decimals. Understanding them helps you check your change and spend your pocket money wisely.
Tenths and hundredths
If you split one whole into 10 equal parts, each part is one tenth, written 0.1. If you split it into 100 equal parts, each is one hundredth, written 0.01.
| Ones | . | Tenths | Hundredths |
|---|---|---|---|
| 0 | . | 4 | 5 |
So 0.45 means 4 tenths and 5 hundredths.
Decimals and money
With money, the first digit after the dot is 10p coins and the second is pennies.
£3.45 = 3 pounds, 4 lots of 10p, and 5 pennies. That is 3 pounds and 45 pence.
Fractions as decimals
Some fractions have easy decimal twins:
| Fraction | Decimal |
|---|---|
| 1/2 | 0.5 |
| 1/4 | 0.25 |
| 3/4 | 0.75 |
Comparing decimals
To compare, line up the dots and check the tenths first, then the hundredths. So 0.7 is bigger than 0.5 because 7 tenths is more than 5 tenths.
Put these decimals in order, smallest first:
- 0.3
- 0.5
- 0.8