To subtract fractions, make sure the bottom numbers (denominators) are the same, then subtract the top numbers (numerators) from one another, retaining the denominator and simplifying if required. This process can be done by hand or by using a calculator.
- Ensure the denominators are the same
Check that the denominators are the same in the fractions that are being subtracted. If they are different, find a number that is divisible by all current denominators. Multiply both the numerator and the denominator by the same number in each fraction to keep the value of the fraction the same. This makes all the denominators the same and allows them to be subtracted. For example, if subtracting 1/6 from 1/2, the denominator in both fractions needs to be 6 because that is the smallest number that is divisible by both. Multiply the numerator and the denominator in 1/2 by 3. The fraction becomes 3/6.
- Subtract the numerators
Subtract the numbers across the top. In this example, 3-1 = 2.
- Keep the same denominator
Put the value of the subtracted numerators over the current denominator. In this example, 2 becomes the numerator, while 6 remains the denominator. The fraction becomes 2/6.
- Simplify the fraction, if necessary
Check the fraction to determine if there is a number that can be divided into both the numerator and the denominator. If there is, divide both the numerator and the denominator by the highest number possible. In this example, 2/6, both 2 and 6 are divisible by 2. Complete this division to simplify the fraction, and the final answer becomes 1/3.