Learn how to add rational, or fractional, numbers by following the tutorial in this video. In the case of fractions where the denominators are the same, the addition is simple: you simply add the numerators and keep the denominator the same. When the denominators are not the same, you need to find the least common denominator (or multiple). Take a look at your denominators and test different numbers to find the smallest multiple of the two. Then, convert the two original fractions so that their denominators have the same multiples. Then, add the numerators straight across to find your answer.