Subtracting fractions with unlike denominators | Summary and Q&A

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September 5, 2015
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Khan Academy
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Subtracting fractions with unlike denominators

TL;DR

Learn how to subtract fractions with different denominators by finding a common multiple and rewriting the fractions.

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Questions & Answers

Q: How do you subtract fractions with different denominators?

To subtract fractions with different denominators, you need to find a common multiple of the denominators and rewrite the fractions using that denominator.

Q: What is the key to finding a common multiple?

The key is to find the least common multiple (LCM) of the denominators. This is the smallest number that both denominators divide into evenly.

Q: Can you explain how to rewrite fractions with a common denominator?

To rewrite a fraction with a common denominator, you multiply both the numerator and denominator by the same factor. This ensures that the value of the fraction remains the same.

Q: How do you simplify the result after subtracting fractions?

After subtracting fractions, simplify the result if possible by finding the greatest common divisor (GCD) of the numerator and denominator and dividing both by it.

Summary & Key Takeaways

  • Fractions with different denominators can be subtracted by finding a common multiple and rewriting the fractions with that denominator.

  • Start by identifying the least common multiple (LCM) of the denominators.

  • Multiply the numerator and denominator of each fraction by the same factor to rewrite them with the common denominator.

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