What mathematical operation is important to perform before adding fractions with unlike denominators?

Finding the least common denominator (LCD) is essential when adding fractions with unlike denominators because it allows you to convert the fractions into equivalent fractions that have a common denominator. When fractions have different denominators, you cannot simply add them together because their sizes are not directly comparable.

The least common denominator is the smallest multiple shared by the denominators of the fractions involved. Once you determine the LCD, you can adjust each fraction by multiplying both its numerator and its denominator by the appropriate factor that will convert its denominator to the LCD. This process creates equivalent fractions that can be easily added together.

For example, if you are adding 1/4 and 1/6, the least common denominator is 12. This means you would convert 1/4 to 3/12 and 1/6 to 2/12. Now, you can add 3/12 and 2/12 to get 5/12. The use of the least common denominator simplifies the addition of fractions and ensures accuracy in the result.