How it is calculated
All calculations use exact whole numbers, and the result is then simplified.
- Add: a/b + c/d = (a×d + c×b) ÷ (b×d)
- Subtract: a/b − c/d = (a×d − c×b) ÷ (b×d)
- Multiply: a/b × c/d = (a×c) ÷ (b×d)
- Divide: a/b ÷ c/d = (a×d) ÷ (b×c)
The answer is simplified by dividing the numerator and denominator by their greatest common divisor (gcd). The minus sign always sits on the numerator. A denominator of 0, or division by a zero fraction, gives an error.
Worked example
- 1/2 + 1/3 = 5/6 (decimal 0.833333)
- 3/4 − 1/4 = 1/2
- 2/3 × 3/4 = 1/2
- 1/2 ÷ 1/4 = 2
- 7/4 as a mixed number = 1 3/4
- −1/2 + 1/3 = −1/6
Why your number may differ
Make sure the numerators and denominators are in the right fields. Only whole numbers are accepted. The decimal is shown to six places, so it may be rounded.