Solution - Long subtraction
40.7
Step-by-step explanation
1. Rewrite the numbers from top to bottom, aligned by their place values
| Place value | hundreds | tens | ones | . | tenths |
| 1 | 2 | 8 | |||
| - | 8 | 7 | . | 3 | |
| . |
Put zeros in the blank number places:
| Place value | hundreds | tens | ones | . | tenths |
| 1 | 2 | 8 | . | 0 | |
| - | 8 | 7 | . | 3 | |
| . |
2. Subtract the numbers using long subtraction method
Because the upper digit (0) in the tenths column is too small to get a positive difference, borrow 1 from the digit (8) in the next number place which becomes (7) and get (10).
| Place value | hundreds | tens | ones | . | tenths |
| 7 | 10 | ||||
| 1 | 2 | 8 | . | 0 | |
| - | 8 | 7 | . | 3 | |
| . |
Subtract the numbers in the tenths column from the top number:
10-0-3=7
| Place value | hundreds | tens | ones | . | tenths |
| 7 | 10 | ||||
| 1 | 2 | 8 | . | 0 | |
| - | 8 | 7 | . | 3 | |
| . | 7 |
Subtract the numbers in the ones column from the top number:
7-7=0
| Place value | hundreds | tens | ones | . | tenths |
| 7 | 10 | ||||
| 1 | 2 | 8 | . | 0 | |
| - | 8 | 7 | . | 3 | |
| 0 | . | 7 |
Because the upper digit (2) in the tens column is too small to get a positive difference, borrow 1 from the digit (1) in the next number place which becomes (0) and get (12).
| Place value | hundreds | tens | ones | . | tenths |
| 0 | 12 | ||||
| 7 | 10 | ||||
| 1 | 2 | 8 | . | 0 | |
| - | 8 | 7 | . | 3 | |
| 0 | . | 7 |
Subtract the numbers in the tens column from the top number:
12-8=4
| Place value | hundreds | tens | ones | . | tenths |
| 0 | 12 | ||||
| 7 | 10 | ||||
| 1 | 2 | 8 | . | 0 | |
| - | 8 | 7 | . | 3 | |
| 4 | 0 | . | 7 |
Write 0 in the hundreds place.
| Place value | hundreds | tens | ones | . | tenths |
| 0 | 12 | ||||
| 7 | 10 | ||||
| 1 | 2 | 8 | . | 0 | |
| - | 8 | 7 | . | 3 | |
| 0 | 4 | 0 | . | 7 |
The solution is: 40.7
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