Read decimals using tenths, hundredths, and thousandths; compare them; and round them. The foundation for all decimal math.
The decimal point separates the whole number from the part that is less than one. Read the number 3.647:
| Ones | . | Tenths | Hundredths | Thousandths |
|---|---|---|---|---|
| 3 | . | 6 | 4 | 7 |
| 3 | 6/10 | 4/100 | 7/1000 |
Key idea: adding a zero at the end of a decimal does not change its value. 0.7 = 0.70 — both are 7 tenths.
1. What is the value of the digit 4 in 2.47?
The first digit after the decimal point is in the tenths place. In 2.47 the digit 4 is immediately after the decimal point, so it is 4 tenths.
2. Which is greater: 0.5 or 0.45?
Write 0.5 as 0.50. Now compare tenths: 5 tenths vs 4 tenths. 5 > 4, so 0.50 > 0.45.
3. Round 3.46 to the nearest tenth.
Look at the hundredths digit: 6. That is ≥ 5, so round the tenths digit up. 3.46 → 3.5.
4. Which number is the smallest?
Compare tenths first. 0.09 has 0 tenths — that is less than all the others which have at least 3 tenths.
5. Round 6.183 to the nearest hundredth.
Look at the thousandths digit: 3. That is < 5, so round down. 6.183 → 6.18.
6. True or false: 0.70 = 0.7
Adding a trailing zero to a decimal does not change its value. 0.70 = 7 tenths = 0.7.
7. Round 4.85 to the nearest tenth.
The hundredths digit is 5 (≥ 5), so round up. 4.85 → 4.9.