How to Multiply and Divide Fractions with Cancellation

The Organic Chemistry Tutor

A clear, step-by-step mathematics tutorial demonstrating how to multiply and divide fractions. The video begins with basic multiplication by multiplying numerators and denominators across. It then introduces the "cancellation method" (simplifying before multiplying) to handle larger numbers more efficiently by breaking them down into factors. This prevents students from having to simplify unwieldy large numbers at the end of the problem. The second half of the video transitions to dividing fractions, introducing the mnemonic "Keep, Change, Flip" to convert division problems into multiplication problems. The narrator demonstrates two examples of this, again utilizing factorization and cancellation to solve the problems efficiently. The video concludes with a concise summary of the two main rules learned. This resource is highly valuable for upper elementary and middle school classrooms as it explicitly models procedural fluency. It moves beyond just getting the answer to showing efficient strategies (cancellation) that build number sense. It is particularly useful for differentiating instruction, offering a standard method for beginners and an advanced method for students ready to manipulate factors.