 # Adding and Subtracting Fractions

Questions

1. Find the lowest common denominator , then add the fractions 2. Find the lowest common denominator, then add the fractions 3. Combine 4. Combine 5. Combine 6. Combine 7. Combine 8. Combine Solutions

1. Technique: prime factor the numerators to determine the LCD (lowest common denominator).  multiply by appropriate numbers to get common denominator simplify now that the denominators are the same , you can add numerators simplify

2. 3. The denominators are already the same. 4. The denominators are already the same. 5. Note: we usually would write 18 = 2 × 9 but since we are going to cancel everything in the numerator , it helps to write
as 18 = 1 × 2 × 9 so we can see that there will still be a 1 left in the numerator.

6. First, convert the mixed numbers to improper fractions since we know how to add improper fractions. Now get a lowest common denominator . Now we can add . 7. 8. First, convert the mixed numbers to improper fractions since we know how to add improper fractions. Now get a lowest common denominator. Now we can add. Prev Next