Grade 6 Math: Subtracting Fractions with Unlike Denominators
TL;DR: Subtraction works just like addition once the denominators match. If they don’t, find the least common denominator, rewrite both fractions to use it, then subtract the numerators and keep the bottom the same. Simplify the result if you can. The whole game is making the pieces the same size before you take anything away, once they match, you are just counting how many of those equal pieces are left. Same toolkit as addition, with a minus sign.
Adding and Subtracting Fractions with Unlike Denominators Calculator
Open the full calculator →Type the problems from this lesson and check each step.
Key takeaways:
- Different denominators mean different-size pieces – you can’t subtract until they match.
- Find the least common denominator (LCD), then rewrite both fractions.
- Subtract the numerators; keep the common denominator.
- Simplify the result by dividing top and bottom by any common factor.
- Example: \(\dfrac{5}{6} – \dfrac{1}{4} = \dfrac{10}{12} – \dfrac{3}{12} = \dfrac{7}{12}\).
Grade 6 focus: Subtracting fractions with unlike denominators uses the same rewriting process as addition: find a common denominator (preferably the LCD), rewrite each fraction, then subtract the numerators.
Video lesson: Watch this Khan Academy tutorial for a clear walk-through.
Method
- Find the LCD of the denominators.
- Rewrite each fraction as an equivalent fraction with that denominator.
- Subtract the numerators; keep the denominator.
- Simplify the result if needed.
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Worked example
Compute \(\frac{7}{10} – \frac{1}{4}\).
\(\mathrm{LCM}(10,4)=20\). Then \(\frac{7}{10} = \frac{14}{20}\) and \(\frac{1}{4} = \frac{5}{20}\). Difference: \(\frac{14}{20} – \frac{5}{20} = \frac{9}{20}\).
Borrowing from the whole
When the first numerator is too small (in mixed-number form), you may need to regroup, borrow \(1\) whole from the integer part and rewrite it as a fraction with the same denominator. That skill pairs directly with this lesson.
Common mistakes
- Subtracting numerators before making denominators match.
- Using an incorrect equivalent fraction when scaling.
- Leaving a negative intermediate step unaddressed when working with mixed numbers.
Fluency check
Try \(\frac{5}{6} – \frac{3}{8}\). LCD \(= 24\): \(\frac{20}{24} – \frac{9}{24} = \frac{11}{24}\).
Recommended EffortlessMath Books
For a workbook that pairs with this page, Mastering Grade 6 Math walks your sixth grader through every grade-6 topic with worked examples and plenty of practice. For more story-problem reps, Mastering Grade 6 Math Word Problems is the matching word-problem book.
Frequently Asked Questions
How do you subtract fractions with unlike denominators?
Find the least common denominator, rewrite both fractions with it, then subtract only the numerators. For 7/10 − 1/4, the LCD of 10 and 4 is 20, so the problem becomes 14/20 − 5/20 = 9/20. Keep the denominator the same and simplify at the end if you can. Here 9/20 is already in simplest form.
How do you subtract fractions with unlike denominators in 6th grade?
In 6th grade you use the least common multiple of the denominators as the LCD. For 5/6 − 1/4, the LCM of 6 and 4 is 12, so 5/6 = 10/12 and 1/4 = 3/12. Then 10/12 − 3/12 = 7/12. Sixth graders may also see answers that are negative, such as 1/6 − 3/4 = 2/12 − 9/12 = −7/12.
What are some examples of subtracting fractions with unlike denominators?
When one denominator divides the other, the larger one is the LCD: 5/8 − 1/2 = 5/8 − 4/8 = 1/8. When they share no factors, multiply them: 2/3 − 1/5 = 10/15 − 3/15 = 7/15. When they share a factor, look for the smallest common multiple: 3/4 − 1/6 = 9/12 − 2/12 = 7/12.
How do you add and subtract fractions with unlike denominators in grade 6?
The first steps are the same for both: find the LCD and rewrite each fraction. Only the last step changes, where you add or subtract the numerators. For 3/4 and 1/6, the LCD is 12, so 3/4 + 1/6 = 11/12 and 3/4 − 1/6 = 7/12. You can check subtraction by adding: 7/12 + 2/12 = 9/12, which equals 3/4.
Are there subtracting unlike fractions worksheets with answers for grade 6?
Yes. The practice problems with this lesson give grade 6 subtraction problems with unlike denominators and answers you can check. Encourage your child to write the LCD above each problem before rewriting, and to watch for the classic mistake of subtracting the denominators, which turns 5/6 − 1/4 into the wrong answer 4/2.
Related EffortlessMath Lessons
If a topic on this page feels rusty, these short lessons go deeper:
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