Decimal Basics – Understanding Decimal Numbers
A decimal is a way of writing numbers that are not whole. The decimal point separates the whole part of a number from the part that is less than one. Decimals are used every single day — in prices, measurements, temperatures, and scores.
Where Do Decimals Come From?
You already know that 1/2 means half of something. A decimal gives us another way to write that same value: 0.5. Both mean exactly the same thing — half.
The Decimal Point
The dot in a decimal number is called the decimal point. Everything to its left is a whole number. Everything to its right is less than one whole.
Example: 34.76
34 is the whole part.
.76 is the decimal part — less than one whole.
Reading Decimals
| Number | How to Read It |
|---|---|
| 0.3 | Zero point three |
| 1.5 | One point five |
| 4.72 | Four point seven two |
| 0.08 | Zero point zero eight |
| 12.005 | Twelve point zero zero five |
Decimals in Everyday Life
- Prices: a loaf of bread costs £1.49
- Measurements: a door is 2.05 m tall
- Temperature: body temperature is 37.5°C
- Sport: a race is won in 9.58 seconds
- Weight: a bag of apples weighs 1.25 kg
The Link Between Decimals and Fractions
| Fraction | Decimal | Meaning |
|---|---|---|
| 1/10 | 0.1 | One tenth |
| 1/100 | 0.01 | One hundredth |
| 1/4 | 0.25 | Twenty-five hundredths |
| 1/2 | 0.5 | Five tenths |
| 3/4 | 0.75 | Seventy-five hundredths |
Zeros After the Decimal Point
Adding zeros at the end of a decimal does not change its value. 0.5 = 0.50 = 0.500. They are all the same. But zeros between the decimal point and other digits DO matter. 0.05 is different from 0.5 — it is ten times smaller.
Key Takeaways
- Decimals are just another way to write fractions and mixed numbers.
- The decimal point separates the whole part from the fractional part.
- Trailing zeros after the last non-zero digit do not change the value.
- Zeros between the decimal point and a digit do change the value.
Practice Questions
- Write 3/10 as a decimal.
- What is the decimal for one and a half?
- Which is bigger: 0.6 or 0.06?
- A book costs four pounds and ninety-nine pence. Write this as a decimal.
- A relay runner finishes in 47.3 seconds. Which part is the whole number and which is the decimal part?