คำตอบ - Long subtraction
คำอธิบายทีละขั้นตอน
1. Rewrite the numbers from top to bottom, aligned by their place values
| Place value | hundreds | tens | ones | . | tenths | hundredths |
| 6 | 8 | 6 | . | 4 | ||
| - | 1 | 9 | 9 | . | 6 | 1 |
| . |
Put zeros in the blank number places:
| Place value | hundreds | tens | ones | . | tenths | hundredths |
| 6 | 8 | 6 | . | 4 | 0 | |
| - | 1 | 9 | 9 | . | 6 | 1 |
| . |
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 digit (4) in the next number place which becomes (3) and get (10).
| Place value | hundreds | tens | ones | . | tenths | hundredths |
| 3 | 10 | |||||
| 6 | 8 | 6 | . | 4 | 0 | |
| - | 1 | 9 | 9 | . | 6 | 1 |
| . |
Subtract the numbers in the hundredths column from the top number:
10-0-1=9
| Place value | hundreds | tens | ones | . | tenths | hundredths |
| 3 | 10 | |||||
| 6 | 8 | 6 | . | 4 | 0 | |
| - | 1 | 9 | 9 | . | 6 | 1 |
| . | 9 |
Because the upper digit (3) in the tenths column is too small to get a positive difference, borrow 1 from the digit (6) in the next number place which becomes (5) and get (13).
| Place value | hundreds | tens | ones | . | tenths | hundredths |
| 5 | 13 | |||||
| 3 | 10 | |||||
| 6 | 8 | 6 | . | 4 | 0 | |
| - | 1 | 9 | 9 | . | 6 | 1 |
| . | 9 |
Subtract the numbers in the tenths column from the top number:
13-6=7
| Place value | hundreds | tens | ones | . | tenths | hundredths |
| 5 | 13 | |||||
| 3 | 10 | |||||
| 6 | 8 | 6 | . | 4 | 0 | |
| - | 1 | 9 | 9 | . | 6 | 1 |
| . | 7 | 9 |
Because the upper digit (5) in the ones 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 (15).
| Place value | hundreds | tens | ones | . | tenths | hundredths |
| 7 | 15 | |||||
| 5 | 13 | |||||
| 3 | 10 | |||||
| 6 | 8 | 6 | . | 4 | 0 | |
| - | 1 | 9 | 9 | . | 6 | 1 |
| . | 7 | 9 |
Subtract the numbers in the ones column from the top number:
15-9=6
| Place value | hundreds | tens | ones | . | tenths | hundredths |
| 7 | 15 | |||||
| 5 | 13 | |||||
| 3 | 10 | |||||
| 6 | 8 | 6 | . | 4 | 0 | |
| - | 1 | 9 | 9 | . | 6 | 1 |
| 6 | . | 7 | 9 |
Because the upper digit (7) in the tens column is too small to get a positive difference, borrow 1 from the digit (6) in the next number place which becomes (5) and get (17).
| Place value | hundreds | tens | ones | . | tenths | hundredths |
| 5 | 17 | |||||
| 7 | 15 | |||||
| 5 | 13 | |||||
| 3 | 10 | |||||
| 6 | 8 | 6 | . | 4 | 0 | |
| - | 1 | 9 | 9 | . | 6 | 1 |
| 6 | . | 7 | 9 |
Subtract the numbers in the tens column from the top number:
17-9=8
| Place value | hundreds | tens | ones | . | tenths | hundredths |
| 5 | 17 | |||||
| 7 | 15 | |||||
| 5 | 13 | |||||
| 3 | 10 | |||||
| 6 | 8 | 6 | . | 4 | 0 | |
| - | 1 | 9 | 9 | . | 6 | 1 |
| 8 | 6 | . | 7 | 9 |
Subtract the numbers in the hundreds column from the top number:
5-1=4
| Place value | hundreds | tens | ones | . | tenths | hundredths |
| 5 | 17 | |||||
| 7 | 15 | |||||
| 5 | 13 | |||||
| 3 | 10 | |||||
| 6 | 8 | 6 | . | 4 | 0 | |
| - | 1 | 9 | 9 | . | 6 | 1 |
| 4 | 8 | 6 | . | 7 | 9 |
The solution is: 486.79
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