Write down the fractions that you will be adding. For example, use 1/6 + 2/5.
Find a common denominator if the denominators are not alike. A common denominator is a number that both denominators will divide into evenly. In order to find a common denominator, write down the multiples of each denominator. Start with five to 10 multiples. Once you write down the multiples, look for a multiple that appears in each denominator's list. In this case, you would write the following multiples for 6: 6 x 1 = 6; 6 x 2 =12; 6 x 3 = 18; 6 x 4 = 24; 6 x 5 = 30; 6 x 6 = 36. You also would write the following multiplies for 5: 5 x 1 = 5; 5 x 2 = 10; 5 x 3 = 15; 5 x 4 = 20; 5 x 5 = 25; 5 x 6 = 30.
The multiple that both denominators share is 30. This also is the lowest value that both denominators will fit into evenly, which is termed the "least common denominator." You can also find a common denominator by multiplying the denominators of the fractions 1/6 and 2/5.
common denominator: 6 x 5 = 30
Rewrite both fractions with the common denominator to get equivalent fractions:
1/6 = 1/6 * 5/5/ = 5/30
2/5 = 2/5 * 6/6/ = 12/30
Add the numerators of the two revised fractions:
5 + 12 = 17.
Place this answer over the common denominator. The answer is 17/30.
If the denominators are the same, you simply add the numerators. For example, find the sum of 1/3 and 1/3.
1/3 + 1/3 = (1 + 1)/3 = 2/3
Simplify your sum if necessary. For instance, the sum of two fractions is 4/8. Divide both numbers by 4 to get a reduced fraction of 1/2.