· Grade 4 lesson · 2 min read
Lesson: What Is a Decimal? (Grade 4)
A decimal shows a part of a whole. The dot separates whole things from the parts.
The dot
In 2.5, the dot is called the decimal point.
- Left of the dot: whole things (2 whole pizzas)
- Right of the dot: parts of one more (half a pizza)
Tenths
Cut one bar into 10 equal pieces. Each piece is one tenth, written 0.1.
3 pieces are colored. That's 3 tenths, or 0.3.
Hundredths
Now cut one square into 100 tiny squares. Each tiny square is one hundredth, written 0.01.
45 tiny squares are colored. That's 45 hundredths, or 0.45.
Decimals are like money
One dollar is the whole. Cents are the parts.
| Money | Decimal | Meaning |
|---|---|---|
| 1 dime | $0.10 | 1 tenth of a dollar |
| 1 penny | $0.01 | 1 hundredth of a dollar |
| 4 dimes and 5 pennies | $0.45 | 45 hundredths of a dollar |
Careful: 0.5 vs 0.05
- 0.5 = 5 tenths = half of the whole (like 50 cents)
- 0.05 = 5 hundredths = a tiny part (like 5 cents)
The position of the digit matters, not just the digit!
Practice
Try the Introduction to Decimals worksheets. Then see how decimals and fractions match in Converting Fractions to Decimals.