How to Add Fractions. Addition of fractions can seem daunting at first. But adding fractions is actually very simple if you understand the basics of denominators. The bottom number in a fraction is called the denominator. The top number in a fraction is called the numerator. In order to add fractions together, they must have the same denominator. If they don't, you need to make them have a common denominator before you can add them together.
Find the lowest common denominator. The lowest common denominator of 2 or more numbers is the smallest whole number that is divisible by each. The easiest way to find the lowest common denominator is to list the multiples of each denominator and then look for the smallest number that appears on all the lists. This is the lowest common denominator.
Re-write the fractions. You will need to re-write each fraction using the lowest common denominator. For example, the lowest common denominator of 1/3, 1/5 and 1/6 is 30. Using the lowest common denominator, 1/3 would become 10/30. 1/5 would be 6/30 and 1/6 would be 5/30.
Add the numerators using the re-written fractions. In the previous equation, 10 plus 6 plus 5 equals 21. Therefore the answer you get when you add the fractions together is 21/30.
Simplify the answer. You will need to reduce the fraction in your answer. In our example, 21/30 can be reduce to 7/10 as both the numerator and the denominator are divisible by 3. To conclude, 1/3, 1/5 and 1/6 add up to 7/10.