How to Calculate Percent Increase and Decrease

Math with Mr. J

This instructional math video guides viewers through the step-by-step process of calculating percent change, covering both percent increases and decreases. The narrator, Mr. J, utilizes a clear formula—subtracting the original value from the new value, dividing by the original value, and multiplying by 100—to determine the percentage of change. The video systematically works through four distinct examples, ranging from simple integer changes to more complex problems involving decimals and rounding. Key themes include the importance of order of operations when setting up the formula, interpreting positive and negative results as increases or decreases respectively, and the technical skill of converting decimals to percentages. The video also addresses special cases, such as percent increases exceeding 100% and scenarios requiring rounding of long decimal answers. The visual aid of a digital blackboard helps students follow the handwritten calculations in real-time. For educators, this resource serves as an excellent tool for introducing or reinforcing the concept of percent change in middle school math curriculums. It provides a reliable procedural model that students can mimic. Teachers can use this video to support lessons on ratios and proportional relationships, specifically standard 7.RP.A.3, by having students pause after each problem setup to perform the calculation themselves before watching the solution.