How this calculator works
Addition combines signed amounts. To recover an unknown addend, subtract the known addend from the sum. Express measured inputs in the same units before adding. Numeric answers retain calculation precision until display.
Formula
s = a + b; a = s - b; b = s - a.
Worked example
12 + 8 = 20. If the sum is 7 and the first addend is -3, the second addend is 7 - (-3) = 10.
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Frequently asked questions
Can I add a negative number?
Yes. Adding -4 has the same effect as subtracting 4.
What happens when one addend is zero?
The sum equals the other addend. Zero is the additive identity.
How can I see the carrying steps?
Long Addition shows a column-by-column explanation for two numbers, including decimal alignment and carries.