Only addition and subtraction need a common denominator. Multiplication and division do not.
To divide, flip the second fraction and multiply — dividing by 2/3 is the same as multiplying by 3/2.
Simplify by dividing top and bottom by their highest common factor.
A denominator of zero has no meaning; nothing can be divided into zero parts.
How do I add fractions with different denominators?
Give them a common denominator by multiplying the two together, rewrite both fractions, add the numerators, then simplify. For 3/4 + 5/6 that is 18/24 + 20/24 = 38/24 = 19/12.
How do I divide one fraction by another?
Flip the second fraction and multiply. So 3/4 ÷ 5/6 becomes 3/4 × 6/5 = 18/20 = 9/10.
How do I turn an improper fraction into a mixed number?
Divide the top by the bottom. The whole-number part is the answer, the remainder stays over the original denominator: 19/12 is 1 remainder 7, so 1 7/12.
How do I convert a fraction to a percentage?
Divide the numerator by the denominator, then multiply by 100. 3/4 is 3 ÷ 4 × 100 = 75%. The "As a percentage" figure above does this for every result automatically.