Subtraction of Fractions With Common Denominators

Deb Russell is a school principal and teacher with over 25 years of experience teaching mathematics at all levels.

Subtracting fractions is easy when you have common denominators. Explain to students that when the denominators—or the bottom numbers—are the same in two fractions, they only need to subtract the numerators or top numbers. The five worksheets below give students plenty of practice subtracting fractions with common denominators.

Each slide provides two printables. Students work the problems and write down their answers on the first printable in each slide. The second printable in each slide provides the answers to the problems to make grading easy.

Worksheet No. 1

In this worksheet, students will subtract fractions with common denominators and reduce them to the smallest terms. For example, in one of the problems, students will answer the problem: 8/9 – 2/9. Since the common denominator is "9," students only need to subtract "2" from "8," which equals "6." They then place the "6" over the common denominator, yielding 6/9.

They then reduce the fraction to its lowest terms, also known as the least common multiples. Since "3" goes into "6" twice and into "9" three times, the fraction reduces to 2/3.

Worksheet No. 2

This printable offers students more practice subtracting fractions with common denominators and reducing them to the smallest terms, or least common multiples.

If students are struggling, review the concepts. Explain that the least common denominator and least common multiples are related. The least common multiple is the smallest positive whole number into which two numbers can be divided evenly. The least common denominator is the smallest least common multiple that the bottom number (denominator) of two given fractions share.

Worksheet No. 3

Before having students answer the problems on this printable, take the time work a problem or two for students as you demonstrate on the chalkboard or a piece of paper.

For example, take an easy calculation, such as the first problem on this worksheet: 2/4 – 1/4. Explain again that the denominator is the number on the bottom of the fraction, which is "4" in this case. Explain to students that since you have a common denominator, they only need to subtract the second numerator from the first, or "2" minus "1," which equals "1." They then place the answer—called the "difference" in subtraction problems—over the common denominator yielding an answer of "1/4."

Worksheet No. 4

Let students know they are more than halfway through their lesson on subtracting fractions with common denominators. Remind them that in addition to subtracting the fractions, they need to reduce their answers to the lowest common terms, which are also called the least common multiples.

For example, the first problem on this worksheet is 4/6 – 1/6. Students place "4 – 1" over the common denominator "6." Since 4 – 1 = 3, the initial answer is "3/6." However, "3" goes into "3" one time, and into "6" twice, so the final answer is "1/2."

Worksheet No. 5

Before students complete this final worksheet in the lesson, have one of them work out a problem on the chalkboard, whiteboard or on a piece of paper as you observe. For example, have a student answer problem No. 15: 5/8 – 1/8. The common denominator is "8," so subtracting the numerators "5 – 1" yields "4/8." Four goes into "4" one time and into "8" twice, yielding a final answer of "1/2."

Russell, Deb. "Subtraction of Fractions With Common Denominators." ThoughtCo, Apr. 5, 2023, thoughtco.com/subtracting-fractions-with-like-denominators-worksheets-2312286. Russell, Deb. (2023, April 5). Subtraction of Fractions With Common Denominators. Retrieved from https://www.thoughtco.com/subtracting-fractions-with-like-denominators-worksheets-2312286 Russell, Deb. "Subtraction of Fractions With Common Denominators." ThoughtCo. https://www.thoughtco.com/subtracting-fractions-with-like-denominators-worksheets-2312286 (accessed September 11, 2024).

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