How to Calculate Percent Increase and Decrease

The Organic Chemistry Tutor

This comprehensive math tutorial provides a step-by-step guide to calculating percent of change, covering both percent increase and percent decrease. The video begins by introducing the core formula: (New Value - Original Value) / Original Value × 100%. The narrator demonstrates this formula with simple numerical examples before progressing to more complex scenarios involving negative results, which indicate a decrease in value. The content explores key themes of identifying variables in word problems, distinguishing between "change to" and "change by," and interpreting positive versus negative percentages. It progresses from basic number sets to real-world applications, including calculating inflation in gas prices, growth in savings accounts, population dynamics, and class enrollment statistics. Special attention is given to parsing word problems where the "new value" must be calculated before applying the percent change formula. For educators, this video serves as an excellent instructional tool for Pre-Algebra and Algebra units on ratios, proportions, and percentages. It effectively addresses common student errors, such as mixing up the new and original values or failing to calculate the total new amount when given only the increment. The clear, handwritten visual style allows students to follow the algorithmic thinking required to solve these problems, making it suitable for direct instruction, review, or flipped classroom assignments.