Addition or subtraction of fractions with the same denominator is easy. Simply add or subtract the numerators on the top row, e.g.: 3/5 + 1/5 = 4/5. But, if the fractions do not have the same denominator, you need to calculate the least common multiple of the denominators. For example, 1/2 + 1/3 = ? The least common multiple of 2 and 3 is 6. The 6 is a multiple of 2 and 3, and it is their smallest common multiple. Thus, converting both fractions to have the same denominator gives 1/2 x 3/3 = 3/6, 1/3 x 2/2 = 2/6. Now you can add the numerators: 3/6 + 2/6 = 5/6. MULTIPLYING FRACTIONS Simply multiply the numerators and denominators of the fractions, e.g.: 1/2 x 4/5 = 4/10. Simplifying the fraction – in this case dividing the numerator and denominator by 2 – gives 2/5.