How to Calculate a Percent of a Number Using Decimals

Math with Mr. J

This instructional math video features Mr. J demonstrating the step-by-step process of finding a percentage of a whole number. Using the specific example of finding 35% of 40, the video breaks down the conceptual meaning of "percent" as "per one hundred" and explains how to translate a word problem into a mathematical equation. Mr. J explicitly models how to convert a percentage into a decimal by dividing by 100 and moving the decimal point two places to the left. The core themes explored include the relationship between percents, fractions, and decimals, as well as the rules for multiplying decimals. The video emphasizes key mathematical vocabulary, such as identifying that the word "of" signifies multiplication in this context. It provides a visual walkthrough of the standard multiplication algorithm, showing how to ignore the decimal point during calculation and correctly place it in the final product based on the number of decimal places in the factors. For educators, this video serves as an excellent direct instruction tool or review resource for units on ratios, proportional relationships, and number systems. It is particularly useful for students struggling with the procedural algorithm for percentage calculations. The clear, handwritten visual style on a blackboard background minimizes distractions, making it appropriate for classroom projection or individual student review to reinforce the connection between percentages and decimal multiplication.