Saturday, February 15, 2014

Elapsed Time


 Elapsed time, and all time concepts, are tricky. Why? For one, time is more abstract. There isn’t an algorithm to turn to in a pinch. Even adding and subtracting time presents problems when going over an hour span. Another reason might be that students have limited clock experiences. I find that students will stand and walk to the door to view the digital clock in the hall rather than use the analog clock hanging in our room. Not many people wear watches anymore with the advent of cell phone clocks. Finally, adults might be to blame. How often do you tell your children, “Three minutes” only to have five or ten go by before you realize it? It happens to me all the time in the classroom. No matter the reason, elapsed time can be especially difficult to master. Here are two of my favorite strategies for teaching elapsed time. The first is elapsed time using a number line. The second is elapsed time using a t-chart. I have found that most students prefer the number line method. Some do not need to make as many "hops" as shown in the video, but rather make larger "hops" of 10 to 15 minutes.  I encourage the students to label ALL elapsed time problems with the words "start time", "end time" and "elapsed time" and to then analyze to see which they are solving for in the problem.










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