Adding and Subtracting Decimals Step-by-Step

Math with Mr. J

This concise instructional video features Mr. J demonstrating the standard algorithm for adding and subtracting decimals. The video breaks down the process into three clear steps: lining up the decimals, inserting placeholder zeros, and performing the operation. Through four distinct examples, the video covers various scenarios, including adding decimals with different place values, adding a whole number to a decimal, subtracting with regrouping, and subtracting a decimal from a whole number. The key themes explored include place value alignment, the function of placeholder zeros, and the concept of "invisible decimals" in whole numbers. The video specifically addresses the common student error of misaligning numbers by justifying right-alignment rather than decimal-alignment. It emphasizes visual organization by rewriting horizontal problems vertically. For educators, this video serves as an excellent direct instruction tool or review resource for 5th and 6th-grade math students. Its clear, uncluttered visual style—resembling a blackboard—focuses entirely on the mechanics of the math without distraction. It effectively scaffolds difficulty, moving from straightforward addition to complex subtraction requiring borrowing across zeros, making it ideal for introducing the topic or remediating students who struggle with algorithm alignment.