The big picture
Each column past the point is a tenth of the last.
| Idea | Remember | Example |
|---|---|---|
| Make a tenth | Cut one whole into ten equal parts. | 0.3 is three tenths. |
| Keep splitting | Ten hundredths make a tenth. Ten thousandths make a hundredth. | 1000 thousandths fill one whole. |
| Read it out | Wholes on the left, parts of one on the right. | 4.07 keeps its zero. |
| Find its spot | A decimal with parts lies between two whole numbers. | 5.3 sits between 5 and 6. |
| Compare two | Wholes, then tenths, then hundredths, then thousandths. | 6.4 is more than 6.25. |
| Swap the name | The column name is the fraction. | 0.25 is 25/100, or 1/4. |
| Add or subtract | Points under points. Fill gaps with a zero. | 2.70 + 1.45 = 4.15. |
| Change the unit | Small to big, divide by the count. Big to small, multiply. | 1350 g is 1.35 kg. |
| Whole plus part | A decimal is its whole part plus a fraction. The bottom is 1, then a zero per digit after the point. | 2.9 is 2 9/10, or 29/10. |
| Borrow | Top digit too small? Borrow from the column on its left. If that column is 0, go one more column left. | 6.20 − 2.85 = 3.35. |
| Look-alike dots | A tenth of an hour is 6 minutes. A ball is not a tenth of an over. An inch is not a tenth of a foot. | 2.4 h is 2 h 24 min. |
Open Part I, Chapter 3 of your textbook. It is A Peek Beyond the Point.