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How to Subtract a Bigger Numerator From a Smaller Numerator

A fraction is a ratio of two whole numbers such as 3/4. The top part of the fraction is referred as a numerator, while the bottom number is the denominator. Adding and subtraction are two basic operations with fractions. However, it is not correct to subtract numerators of any two fractions unless their denominators are equal. If they are not equal you have to calculate the common denominator before the subtraction.

Instructions

- 1
  Multiply the fraction with the larger numerator by the denominator of the second fraction. For example, if the two fractions are 7/9 and 3/4 then you transform the first fraction as follows: (7/9) x 4 = (7x4) / (9x4) = 28/36.
- 2
  Multiply the fraction with the smaller numerator by the denominator of the first fraction. In this example, the second fraction is 3/4; (3/4) x 9 = (3x9)/(4x9) = 27/36. Note that the denominator (36) is the same for both transformed fractions and is referred as the common denominator for these fractions.
- 3
  Subtract the numerator of the second fraction from the numerator of the first fraction. In this example, the result is 28/36 - 27/36 = 1/36.

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