How to Add Fractions with Unlike Denominators

The Organic Chemistry Tutor

This instructional math video provides a clear, step-by-step tutorial on how to add fractions with unlike denominators. The narrator utilizes a digital whiteboard to demonstrate the mathematical procedure for finding a common denominator, which is a critical prerequisite for adding fractions that have different bottom numbers. The video covers two distinct examples: adding 2/3 + 1/4 and adding 1/5 + 2/7, ensuring viewers see the method applied to different sets of numbers. The core theme focuses on the concept of equivalent fractions and the necessity of common denominators in arithmetic operations. The video explicitly breaks down the process of multiplying the numerator and denominator of one fraction by the denominator of the other—a reliable algorithm for students who struggle to find the Least Common Multiple (LCM) mentally. It also touches briefly on the final step of simplifying fractions, although the examples chosen do not require reduction. For educators, this video serves as an excellent resource for direct instruction, remediation, or a flipped classroom model for upper elementary and middle school math students. It isolates the specific skill of creating common denominators without the distraction of complex word problems or mixed numbers. Teachers can use this video to visually reinforce the algorithm after conceptual understanding has been established with manipulatives, or as a reference tool for students to review independently while completing homework.