How to Subtract Fractions with Different Denominators

The Organic Chemistry Tutor

This instructional video provides a clear, step-by-step tutorial on how to subtract fractions with unlike denominators. The narrator demonstrates the process using two specific examples: 7/8 minus 3/5 and 4/9 minus 1/7. The core method taught involves finding a common denominator by multiplying the two existing denominators together, rather than searching for the Least Common Multiple (LCM), ensuring a straightforward algorithmic approach for students. The video explores key mathematical themes including finding common denominators, creating equivalent fractions, and performing subtraction with numerators. It visually emphasizes the mechanics of cross-multiplying to adjust the numerators while keeping the denominators consistent. The digital whiteboard format allows viewers to follow the handwriting in real-time, making the abstract steps concrete and followable. For educators, this video serves as an excellent direct instruction tool or a review resource for students struggling with fraction operations. It eliminates the initial hurdle of finding the LCM, allowing students to focus on the process of converting fractions and subtracting them. It is particularly useful for 5th and 6th-grade math classrooms where operations with rational numbers are a primary focus.