How to Subtract Three Fractions with Different Denominators

The Organic Chemistry Tutor

This educational math video provides a clear, step-by-step tutorial on how to subtract three fractions that have different (unlike) denominators. The narrator demonstrates two distinct examples, guiding viewers through the process of finding a common denominator, converting the fractions into equivalent forms, performing the subtraction across the numerators, and finally simplifying the resulting fraction to its lowest terms. The video utilizes a digital blackboard format with color-coded handwriting to distinguish between the original problem and the calculation steps. The key themes explored include finding common denominators using two methods: multiplying all denominators together and finding the Least Common Multiple (LCM). The video also emphasizes arithmetic fluency, specifically multi-digit multiplication and subtraction, as well as the crucial final step of simplifying fractions. The narrator models mathematical thinking by vocalizing mental math strategies and self-correcting calculation checks in real-time. For educators, this video serves as an excellent resource for demonstrating procedural fluency in fraction operations. It bridges the gap between simple two-fraction subtraction and more complex multi-term operations. Teachers can use this video to differentiate instruction for advanced students ready for multi-step problems or as a review tool for students struggling with the algorithm of finding common denominators. The clear visual layout helps students organize their own work when solving similar problems.