When the top digit is too small
A tank has 6.2 L of water. You pour out 2.85 L. How much is left?
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Step 1 of 4
- 6.2 is written 6.20. The points line up.
- 0 hundredths is less than 5. Break 1 tenth into 10 hundredths.
- 10 − 5 = 5. Now 1 tenth is less than 8. Break 1 whole into 10 tenths.
- 11 − 8 = 3, and 5 − 2 = 3. The answer is 3.35.
The rule
6.20 − 2.85 = 3.35, so 3.35 L is left.
Subtract column by column, from the right. To borrow is to break one into ten smaller parts. Top digit too small? Borrow from the column on its left. If that column is 0, go one more column left.
One whole is 10 tenths. One tenth is 10 hundredths.
Write zeros so both numbers end in the same column. Then check by adding back: 3.35 + 2.85 = 6.20.
| Take away | Zeros added | What you break | Answer |
|---|---|---|---|
| 4.5 − 1.8 | none | 1 whole into tenths | 2.7 |
| 9 − 3.46 | 9.00 | a whole, then a tenth | 5.54 |
| 8.4 − 2.375 | 8.400 | a tenth, then a hundredth | 6.025 |