wikiHow Adding and Subtracting Fractions Calculator To add or subtract fractions, you need to have a common denominator. For adding fractions: 1. Determine the denominators of the fractions to be added. 2. Find the least common multiple (LCM) of the denominators. 3. Rewrite each fraction with the LCM as the denominator. 4. Add the numerators of the fractions together. 5. Simplify the fraction if possible by reducing to lowest terms. For subtracting fractions: 1. Determine the denominators of the fractions to be subtracted. 2. Find the least common multiple (LCM) of the denominators. 3. Rewrite each fraction with the LCM as the denominator. 4. Subtract the numerators of the fractions. 5. Simplify the fraction if possible by reducing to lowest terms. Here's an example to help illustrate the process: Adding fractions: 1/3 + 2/5 Step 1: Determine the denominators of the fractions, which are 3 and 5. Step 2: Find the least common multiple (LCM) of 3 and 5, which is 15. Step 3: Rewrite each fraction with the LCM as the denominator. 1/3 = (1 x 5) / (3 x 5) = 5/15 2/5 = (2 x 3) / (5 x 3) = 6/15 Step 4: Add the numerators of the fractions together. 5/15 + 6/15 = 11/15 Step 5: Simplify the fraction if possible. 11/15 is already in its simplest form. So 1/3 + 2/5 = 11/15. Subtracting fractions: 3/4 - 1/2 Step 1: Determine the denominators of the fractions, which are 4 and 2. Step 2: Find the least common multiple (LCM) of 4 and 2, which is 4. Step 3: Rewrite each fraction with the LCM as the denominator. 3/4 = (3 x 1) / (4 x 1) = 3/4 1/2 = (1 x 2) / (2 x 2) = 2/4 Step 4: Subtract the numerators of the fractions. 3/4 - 2/4 = 1/4 Step 5: Simplify the fraction if possible. 1/4 is already in its simplest form. So 3/4 - 1/2 = 1/4. Alternatively, you can use an online adding and subtracting fractions calculator to quickly add or subtract fractions by inputting the fractions. Page