Vertically align numbers with Larger Number on top:
| 1 | . | 0 | 0 | |
| − | 0 | . | 9 | 9 |
Subtract using place value:
| Ones | Tenths | Hundredths | ||
|---|---|---|---|---|
| 9 | ||||
| 0 | 10 | 10 | ||
| 1 | 1 | . | 0 | 0 |
| 0.99 | 0 | . | 9 | 9 |
| Difference | 0 | . | 0 | 1 |
Column traversal from right to left
Hundredths column:
Hundredths column:
- Since 0 is less than 9, we have to borrow 1 from the Tenths column
- As a result, 0 becomes 10, and 10 − 9 = 1
- The 0 in the Tenths column becomes 9 after borrowing 1 from its regrouped value of 10
Tenths column:
- 9 − 9 = 0
- Because it was the first nonzero digit to the left of the 0 in the Hundredths column, the 1 in the Ones column became 0 after 1 was borrowed for the purpose of regrouping the 0 in the Tenths column (borrowing across a 0)
Ones column:
- 0 − 0 = 0
| 9 | ||||
| 0 | 10 | 10 | ||
| 1 | . | 0 | 0 | |
| − | 0 | . | 9 | 9 |
| 0 | . | 0 | 1 |
Therefore, the Difference between 1 and 0.99 is 0.01
Check computation by comparing Larger Number and the Sum of Smaller Number and Difference:
| 1 | 1 | |||
| 0 | . | 9 | 9 | |
| 0 | . | 0 | 1 | |
| 1 | . | 0 | 0 |
Sum of Smaller Number and Difference = 1 (trailing zeros are dropped)
Sum of Smaller Number and Difference = Larger Number (1 = 1) ✓
