Solution - Long subtraction
Step-by-step explanation
1. Rewrite the numbers from top to bottom, aligned by their place values
| Place value | hundreds | tens | ones | . | tenths | hundredths | thousandths |
| 1 | 8 | 0 | |||||
| - | 9 | 4 | . | 3 | 8 | 5 | |
| . |
Put zeros in the blank number places:
| Place value | hundreds | tens | ones | . | tenths | hundredths | thousandths |
| 1 | 8 | 0 | . | 0 | 0 | 0 | |
| - | 9 | 4 | . | 3 | 8 | 5 | |
| . |
2. Subtract the numbers using long subtraction method
Because the upper digit (0) in the thousandths column is too small to get a positive difference, borrow 1 from the number to the left (80.00) which becomes (79.99) and get (10).
| Place value | hundreds | tens | ones | . | tenths | hundredths | thousandths |
| 7 | 9 | 9 | 9 | 10 | |||
| 1 | 8 | 0 | . | 0 | 0 | 0 | |
| - | 9 | 4 | . | 3 | 8 | 5 | |
| . |
Subtract the numbers in the thousandths column from the top number:
10-0-5=5
| Place value | hundreds | tens | ones | . | tenths | hundredths | thousandths |
| 7 | 9 | 9 | 9 | 10 | |||
| 1 | 8 | 0 | . | 0 | 0 | 0 | |
| - | 9 | 4 | . | 3 | 8 | 5 | |
| . | 5 |
Subtract the numbers in the hundredths column from the top number:
9-8=1
| Place value | hundreds | tens | ones | . | tenths | hundredths | thousandths |
| 7 | 9 | 9 | 9 | 10 | |||
| 1 | 8 | 0 | . | 0 | 0 | 0 | |
| - | 9 | 4 | . | 3 | 8 | 5 | |
| . | 1 | 5 |
Subtract the numbers in the tenths column from the top number:
9-3=6
| Place value | hundreds | tens | ones | . | tenths | hundredths | thousandths |
| 7 | 9 | 9 | 9 | 10 | |||
| 1 | 8 | 0 | . | 0 | 0 | 0 | |
| - | 9 | 4 | . | 3 | 8 | 5 | |
| . | 6 | 1 | 5 |
Subtract the numbers in the ones column from the top number:
9-4=5
| Place value | hundreds | tens | ones | . | tenths | hundredths | thousandths |
| 7 | 9 | 9 | 9 | 10 | |||
| 1 | 8 | 0 | . | 0 | 0 | 0 | |
| - | 9 | 4 | . | 3 | 8 | 5 | |
| 5 | . | 6 | 1 | 5 |
Because the upper digit (7) 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 (17).
| Place value | hundreds | tens | ones | . | tenths | hundredths | thousandths |
| 0 | 17 | ||||||
| 7 | 9 | 9 | 9 | 10 | |||
| 1 | 8 | 0 | . | 0 | 0 | 0 | |
| - | 9 | 4 | . | 3 | 8 | 5 | |
| 5 | . | 6 | 1 | 5 |
Subtract the numbers in the tens column from the top number:
17-9=8
| Place value | hundreds | tens | ones | . | tenths | hundredths | thousandths |
| 0 | 17 | ||||||
| 7 | 9 | 9 | 9 | 10 | |||
| 1 | 8 | 0 | . | 0 | 0 | 0 | |
| - | 9 | 4 | . | 3 | 8 | 5 | |
| 8 | 5 | . | 6 | 1 | 5 |
Write 0 in the hundreds place.
| Place value | hundreds | tens | ones | . | tenths | hundredths | thousandths |
| 0 | 17 | ||||||
| 7 | 9 | 9 | 9 | 10 | |||
| 1 | 8 | 0 | . | 0 | 0 | 0 | |
| - | 9 | 4 | . | 3 | 8 | 5 | |
| 0 | 8 | 5 | . | 6 | 1 | 5 |
The solution is: 85.615
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