Adding Unlike Fractions Mentally Using Cross Multiplication

MatholiaChannel

This educational video demonstrates a specific mental math strategy for adding fractions with unlike denominators, often referred to as the "cross multiplication" or "butterfly" method. Through three distinct examples of increasing complexity, the narrator guides viewers through a consistent three-step process: multiplying the denominators to find a common base, cross-multiplying the numerators with opposite denominators, and adding the results to find the final numerator. The video covers key concepts including identifying numerators and denominators, performing mental multiplication, and simplifying results. It progresses from simple proper fractions to examples that result in improper fractions, showing how to convert the final answer into a mixed number. The visual presentation uses color-coded highlights (pink underlines, green and red circles) to clearly track which numbers are being operated on at each stage. For educators, this video serves as an excellent tool for introducing a procedural shortcut for fraction addition or for reinforcing mental math fluency. It is particularly useful for students who struggle with the traditional method of finding the Least Common Multiple (LCM). The step-by-step visual scaffolding makes the abstract process concrete, allowing teachers to pause and predict values, making it ideal for whole-class instruction or independent review stations.