Solution - Long subtraction
10.21
Step-by-step explanation
1. Rewrite the numbers from top to bottom, aligned by their place values
| Place value | tens | ones | . | tenths | hundredths |
| 2 | 0 | ||||
| - | 9 | . | 7 | 9 | |
| . |
Put zeros in the blank number places:
| Place value | tens | ones | . | tenths | hundredths |
| 2 | 0 | . | 0 | 0 | |
| - | 9 | . | 7 | 9 | |
| . |
2. Subtract the numbers using long subtraction method
Because the upper digit (0) in the hundredths column is too small to get a positive difference, borrow 1 from the number to the left (20.0) which becomes (19.9) and get (10).
| Place value | tens | ones | . | tenths | hundredths |
| 1 | 9 | 9 | 10 | ||
| 2 | 0 | . | 0 | 0 | |
| - | 9 | . | 7 | 9 | |
| . |
Subtract the numbers in the hundredths column from the top number:
10-0-9=1
| Place value | tens | ones | . | tenths | hundredths |
| 1 | 9 | 9 | 10 | ||
| 2 | 0 | . | 0 | 0 | |
| - | 9 | . | 7 | 9 | |
| . | 1 |
Subtract the numbers in the tenths column from the top number:
9-7=2
| Place value | tens | ones | . | tenths | hundredths |
| 1 | 9 | 9 | 10 | ||
| 2 | 0 | . | 0 | 0 | |
| - | 9 | . | 7 | 9 | |
| . | 2 | 1 |
Subtract the numbers in the ones column from the top number:
9-9=0
| Place value | tens | ones | . | tenths | hundredths |
| 1 | 9 | 9 | 10 | ||
| 2 | 0 | . | 0 | 0 | |
| - | 9 | . | 7 | 9 | |
| 0 | . | 2 | 1 |
Write 1 in the tens place.
| Place value | tens | ones | . | tenths | hundredths |
| 1 | 9 | 9 | 10 | ||
| 2 | 0 | . | 0 | 0 | |
| - | 9 | . | 7 | 9 | |
| 1 | 0 | . | 2 | 1 |
The solution is: 10.21
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