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Math for Kids23 chapters | 325 lessons

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Instructor:
*Nola Bridgens*

Nola has taught elementary school and tutored for four years. She has a bachelor's degree in Elementary Education, a master's degree in Marketing, and is a certified teacher.

How can we compare fractions that don't share the same denominator? By finding a common denominator for each fraction! In this lesson, you will learn how to find the least common denominator which will then allow you to compare fractions with unlike denominators.

Fractions consist of a numerator and a denominator. The **numerator** is the top number of a fraction that tells how many pieces of the whole we are talking about. The **denominator** is the bottom number of a fraction and it tells how many *total* pieces make up one whole. How do you compare fractions when they don't have the same denominator? You have to find common denominators.

A **common denominator** is a multiple that both denominators share. To compare fractions with unlike denominators, you need to find the **least common denominator (LCD)**, or the smallest multiple the denominators share.

So, what fraction of your favorite candy bar would be more, 2/3 or 4/5? The two fractions have different denominators, so we need to find the LCD.

The first step is to list the multiples of each denominator:

Multiples of 3: 3, 6, 9, 12, 15, 18

Multiples of 5: 5, 10, 15, 20

The first multiple both 3 and 5 share is 15, so we need to make equivalent fractions with denominators of 15.

**Equivalent fractions** are fractions that represent the same part of the whole. To find an equivalent fraction, you multiply the numerator and the denominator by the same number.

In our example, we need to make 2/3 and 4/5 both have a denominator of 15. We can multiply 2/3 by 5/5 and 4/5 by 3/3 to find equivalent fractions with denominators of 15.

Now that both fractions have the same denominator, we can easily compare them.

When fractions have the same denominator, the larger fraction is the one with the larger numerator. If the numerators are the same, the fractions are equivalent fractions.

In our example, 12/15 is larger than 10/15, so 4/5 of the candy bar would be more. You would tell your mom that you would like 4/5 of your favorite candy bar, please.

The image shows what 10/15 and 12/15 look like.

Compare 3/8 and 1/2. Which fraction is larger? Try this problem by yourself and then look at the solution.

The denominators are different, so the first step is to list the multiples of each number.

Multiples of 8: 8, 16 24

Multiples of 2: 2, 4, 6, 8, 10

The first multiple they share or LCD is 8. Since 3/8 already has a denominator of 8 we can leave it alone.

The next step is to find an equivalent fraction for 1/2 that has a denominator of 8. If we multiply both the numerator and denominator by 4 we get 4/8.

Next, we look at the two fractions, 3/8 and 4/8, and the fraction with the larger numerator is the bigger fraction. 4/8 is more than 3/8, so 1/2 is more than 3/8.

We can compare fractions with unlike denominators by finding the **least common denominator** and making **equivalent fractions**. When the **denominators** are the same, the number with the larger **numerator** is the larger fraction.

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Math for Kids23 chapters | 325 lessons

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