Finding and Estimating Elapsed Time Using Number Lines and Subtraction

Sheena Doria

This comprehensive math tutorial guides students through the concepts of calculating and estimating elapsed time. Narrated by an animated teacher, the video breaks down two primary methods for finding the duration between two times: using a number line and using subtraction. It covers essential prerequisite knowledge, including reading digital clocks, understanding the difference between A.M. and P.M., and knowing that one hour equals 60 minutes. The video explores several key themes, such as regrouping (borrowing) when subtracting time, where students must convert one hour into 60 minutes rather than the standard base-10 borrowing. It also addresses how to calculate elapsed time when an event crosses from morning to afternoon (A.M. to P.M.) by converting the end time to a 24-hour format (adding 12 hours). Additionally, the video teaches estimation strategies by rounding times to the nearest ten minutes before calculating. For educators, this video is an excellent resource for 3rd through 5th-grade math instruction. It provides clear, step-by-step visualizations of algorithms that can be difficult for students to grasp abstractly. The inclusion of word problems involving chores, studying, and working makes the content relatable. Teachers can use this video to introduce the concept of elapsed time, demonstrate the specific mechanics of 'borrowing' time, or review strategies for solving complex time intervals involving the 12-hour clock boundary.