Q:

# How do you find the common denominator?

A:

Find the common denominator of a set of fractions by identifying the denominators of the fractions, creating a list of the multiples of those denominators, and then choosing the smallest multiple that both denominators share. The common denominator is used to add or subtract fractions that originally had different denominators.

## Keep Learning

1. Find the denominators of the fractions

The denominator is the bottom number in a fraction. For example, if the fractions are 3/5 and 1/7, then 5 and 7 are the denominators.

2. List the multiples of the denominators

Make a list of the first ten multiples of the denominators. In the example from Step 1, the first ten multiples of 5 are 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50. The first ten multiples of 7 are 7, 14, 21, 28, 35, 42, 49, 56, 63 and 70.

3. Choose the lowest multiple that both denominators share

Look at the list of multiples for the denominators and choose the one that is the same in both lists. In the example, the number 35 is in both lists so that is the common denominator. If there is no shared number, continue listing multiples until there is a number that is the same in both lists. The easiest way to find this for just two fractions is to multiply the original denominators together.

Sources:

## Related Questions

• A: To multiply improper fractions, multiply the fractions' numerators by each other for the product numerator, and multiply the denominators by each other for... Full Answer >
Filed Under:
• A: A chart of all products for multiples up to 100 is available at NCalculators.com. Many other websites offer charts for smaller multiples, including FactorZ... Full Answer >
Filed Under:
• A: There are infinite multiples of 19, but 10 of them are 19, 38, 57, 76, 95, 114, 133, 152, 171 and 190. Multiples of a number are products of that number an... Full Answer >
Filed Under:
• A: The multiples of 48 are 48, 96, 144, 192, 240, 288, 336, 384, 432, 480 and so on. According to MathWorld, the multiple of any number is that number times a... Full Answer >
Filed Under:
PEOPLE SEARCH FOR