How it works
A mixed number (a whole number plus a fraction, like 2 3/4) is first converted to a single improper fraction before any calculation.
Addition and subtraction convert both fractions to a common denominator; multiplication multiplies straight across; division multiplies by the second fraction flipped upside down.
Every result is reduced to its lowest terms by dividing both sides by their greatest common divisor, so equivalent answers are always shown the same way.
Formula: a/b + c/d = (a×d + c×b) / (b×d), and similarly for subtract, multiply and divide.
Examples
Adding two fractions
1/2 + 1/3 = (1×3 + 1×2) / (2×3) = 5/6.
Subtracting mixed numbers
2 3/4 − 1 1/2 = 11/4 − 3/2 = 5/4, which is 1 1/4.
Things to keep in mind
- Leave the whole-number field blank (or zero) for a plain fraction rather than a mixed number.
- Dividing by a fraction equal to zero is rejected, the same as dividing by zero anywhere else.
- The denominator of either fraction cannot be zero.