How this calculator works
Align decimal points by expressing both inputs with the same number of decimal places. For equal signs, add magnitudes with carries; for opposite signs, subtract the smaller magnitude with borrowing and restore the sign. Reverse modes rearrange the original equation, then show the corresponding column operation. Integer coefficients preserve exact decimal results.
Formula
c = a - b; a = c + b; b = a - c. Borrow one unit from the next place whenever a column difference would be negative.
Worked example
1002 - 487 = 515. Borrowing passes through the zero tens and hundreds columns. For decimals, 10.05 - 0.8 = 9.25 after aligning decimal places.
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Frequently asked questions
Can I enter decimals?
Yes. Decimal places are aligned before calculation, so 0.1 and 0.20 use the same place-value scale.
How are negative inputs handled?
The column work uses magnitudes with the appropriate addition or subtraction. The exact answer restores the final sign.
Why show the answer as text?
Exact decimal text avoids binary rounding artefacts and preserves every result digit supported by the numeric input values.