# How to Add and Subtract Fractions

Once you know the trick to adding and subtracting fractions with different denominators, you'll have no problem with these problems.

Close
X
Playback

### Up next in Basic Math Skills (15 videos)

Do you and arithmetic add up to disaster? Sharpen your basic bath skills with the lessons in this Howcast video series.

#### You Will Need

• Two fractions
• A pencil and paper

## Steps

1. Step 1

#### Add fractions with same denominator

Add or subtract the numerators and keep the same denominator if the fractions have the same denominator.

2. The numerator is the number on the top, and the denominator the number on the bottom of the fraction.

3. Step 2

#### Find a common denominator

Find the lowest common denominator to both fractions if they have different denominators. For example, if you add 1/3 plus 3/8, the least common denominator is 24, since three times eight equals 24.

4. The lowest common denominator is the smallest common multiple of both denominators.

5. Step 3

#### Rewrite the fractions

Rewrite the fractions, using the lowest common denominator. Multiply the numerator by the same number by which you multiplied the denominator.

6. Step 4

#### Add or subtract the numerators

Add or subtract the numerators and write the sum over the common denominator. The sum of 9/24 and 8/24 is 17/24. The difference is 1/24.

7. Step 5

#### Reduce the fraction

If necessary, reduce the fraction by dividing the numerator and denominator by the highest number you can.

8. A fraction in which the numerator is larger than the denominator is called an improper fraction.