It all Adds up with Time

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SWBAT convert units of time and calculate elapsed time.

Big Idea

The students are working on the concept of adding and subtracting time along with developing their own strategies to figure out elapsed time.


10 minutes

The students will be completing 3 problems involving conversions in the customary system.  This is a review for students.  Students can check with a partner to see if there answers are correct.  After completion of the Do Now, I will direct students to the essential question for the day:  what are the standard units of measurement for time, how can we use the standard units of time to add and subtract with time and what is elapsed time?

Learning about time

65 minutes

The direct instruction begins by talking about time and its standard units of measurement.  The mathematical problems will involve using the equal sign and combining like terms.(SMP 2) Once this is established, the students will be looking at adding and subtracting time. There are several problems in the power point to use to help students practice this concept.  I drew lines in between the units of measurement to help students realize that it is similar to place value.(SMP 5)  We add hours to hours, minutes to minutes, and seconds to seconds. I ask students when have they combined common place values together in their prior learning (base 10).  Then I ask them what they did when they had too much or too little in a place value (regrouped the numbers).  Then we look at regrouping with time.  This is when the conversions for time take place. We go through several problems together.  Upon completion of the direct and guided instruction, I will ask the students how adding and subtracting time is like base 10 number system and how it is different.(SMP 7)  The next step is to have them work independently.  I’ve attached an activity title White board.  I like to have students work on the white boards because it allows me to visually check all students at once.  I can really zero in on who is getting and who is not.  I will do as many problems as needed to make sure they have this concept down solid. Following the white board activity, I will go back to the notes to talk about elapsed time.  I will give the students the definition , but ask them to come up with the strategy to figuring it out.  As students work through coming up with a strategy, I’m going to give them several scenarios (with answers) to check their strategy out.(SMP 3)  I will continually ask them if their strategy works for all problems.  As students finish developing their own strategies, I will have them share in pairs and then whole group.  The students will be able to respond to each other’s strategies.  Finally, the students will work with their tablemates to complete an activity called Elapsed time round table  (SMP 1,2,3)


10 minutes