When my students do their homework, I tell them to put B.T. (beginning time) on the top of their papers, then write the time they begin their homework. When they finish, they write E.T. (ending time) and write the time they finished. I don't tell them to solve it at first; I just want them to develop the habit of writing it. This helps build background knowledge of passing time. By the time I'm ready to introduce a formal unit on elapsed time, students have a working definition of elapsed time meaning "how long it takes," or "how much time passed." Then we try various strategies for solving so they can choose the one that works best for them.
When my students do their homework, I tell them to put B.T. (beginning time) on the top of their papers, then write the time they begin their homework. When they finish, they write E.T. (ending time) and write the time they finished. I don't tell them to solve it at first; I just want them to develop the habit of writing it. This helps build background knowledge of passing time. By the time I'm ready to introduce a formal unit on elapsed time, students have a working definition of elapsed time meaning "how long it takes," or "how much time passed." Then we try various strategies for solving so they can choose the one that works best for them.