Beyond Just Addition
- Students will use addition strategies in the context of solving elapsed time word problems.
- Lead the students in a quick brainstorm of events that have starting and ending times (e.g. school schedule, sports events, airplane flights, etc.).
- Tell the students that they are going to be learning how to calculate elapsed time, which is the amount of time that passes between two different times.
Explicit Instruction/Teacher modeling(5 minutes)
- Write the following problem on the board: Judy arrived at the movie theater at 1:30. When the movie finished, it was 3:15. How much time did Judy spend at the movie theater?
- Using a large model clock, show the students how you can find the starting time of 1:30.
- Demonstrate the process of counting one hour and 45 minutes to show the amount of time that had passed. Show the students how to start at 1:30 and move ahead one hour, counting by five to find the end time.
- Model using a number line to find the elapsed time. Explain that the start time should be labeled on the left side, or the beginning, of the number line, and the end time should be on the right side, or the end, of the number line. Think aloud and determine the marks and intervals that are most appropriate for this context (e.g., counting by intervals of 10 minutes).
Guided Practice(10 minutes)
- Invite the students to participate in using clocks to add on and count the hours and minutes between two different times.
- Distribute individual student clocks, individual whiteboards, and whiteboard markers.
- Write the following problem on the board: Mary went to the mall at 5:15. She finished shopping at 8:45. How long did Mary spend shopping?
- Guide the students through the process of finding the elapsed time.
- Display additional problems and have students work with a partner to find the elapsed time. Example problems include:
- Laticia made dinner for her family. She put it in the oven at 4:50 and it was done at 6:00. How long did it take to cook dinner?
- Nico's soccer game started at 9:00 and it ended at 10:15. How long did the soccer game last?
Independent working time(15 minutes)
- Ask students to complete the How Long? worksheet.
- Monitor students and provide additional practice and help, as needed.
Enrichment: Invite students to complete the Airport Schedule worksheet
- If students have difficulty with adding both hours and minutes, teach the concepts of adding hours and minutes separately.
- Guide the students through several more problems before independent work time.
- For students who have difficulty telling time, label the minutes on the clock in increments of five or invite students to create their own model clock.
- Consider using the number line method to help students find the elapsed time.
- In place of using a large model clock, use a website that has an interactive clock (link in resources).
- Ask all students to create the time, 4:00 on their clocks.
- Write the following sentences on the board: The soccer game ended at 7:30. How long did the game last?
- Ask students to calculate the length of the game and show the time on their individual clocks. Then, they should write their answers on their individual whiteboards along with a number line that shows their work.
Review and closing(5 minutes)
- Ask students to consider the following questions:
- What are some times in your life that finding elapsed time will be helpful?
- What strategy worked best for you as you calculated the elapsed time?
- How would you teach someone else to find elapsed time?
- Facilitate a class discussion with these questions as a guide.