Elapsed Time: Using a Timeline to Determine Elapsed Time

• Lesson
3-5
1

Students learn to calculate elapsed time by using a timeline, and then complete three engaging and fun activities that plan a circus performance, their class schedule, and their day.

This lesson explores elapsed time through the use of timelines. Students will use timelines to mark start times and end times of given activities, and will interpret the timelines to understand how to calculate elapsed time.  With the exception of the Timeline Activity Sheet, you will want to make sure that each student has one copy of each activity sheet. Make multiple copies of the Timeline Activity Sheet so that each student can have at least 3 copies.

Begin class with a discussion about elapsed time. Ask students, "What is elapsed time and when do we need to measure it?" [Elapsed time is the length of time between a start time and an end time. You might use it to find how long a movie lasts, or the length of time it took to walk between two locations.]

After an initial discussion, distribute two copies of the Elapsed Time Timelines Activity Sheet to each student. State the current time as the starting time of the activity, and write it on the board. When the activity is completed, you will ask the students what time it is so they will be calculating the elapsed time of the activity. There are two separate timelines on each page, so each page can be used twice. Display an overhead of the activity sheet and point out that the timeline begins at midnight and ends 24 hours later at midnight. Select a student and tell the class that on Saturday, that student began cleaning their room at 7:00 a.m. Ask students to draw an arrow pointing to 7:00 a.m. on the timeline and label it "Start," as shown below.

Quickly check students' work to ensure that they are placing the arrow in the correct location, and then, draw the arrow on the overhead version. Tell the class that the student cleaned their room until 10:00 a.m. Have them place at arrow at 10:00 a.m. and label it "Finish," and pause before drawing it on the overhead. Explain to students that they can use this timeline to measure elapsed time by counting forward as they would on a number line.

Demonstrate that students can count time by 5 minutes using the smallest tick marks, 15 minutes using the medium tick marks, and hours using the largest tick marks. Ask them how much time has elapsed between when the student started and finished cleaning her room. [Three hours have elapsed.] Now, have the start time by 8:15 a.m. and the finish time be 10:20 a.m. Ask students, "How much time has elapsed?" [2 hours and 5 minutes have elapsed.] Lastly, give students a starting time of 11:45 a.m. and a finishing time of 1:05 p.m. Ask students, "How much time has elapsed?" [1 hour and 20 min. have elapsed.] Follow up each scenario with the question, "How did you know?" Students should have different increments of time that they count by: 5 minutes, 10 minutes, 15 minutes, 30 minutes, and/or 1 hour.

Tell students that they will be completing activities involving elapsed time with a partner. Depending on your class, you may want to pair students according to ability or let them choose their own partner. The activity sheets, in order, should be Circus Manager, My Day, and Class Schedule. Circus Manager measures elapsed time, while My Day and Class Schedule apply elapsed time to determine an end time. My Day is less difficult than Class Schedule, so distribute these activities accordingly, if differentiation is needed (or if time is an issue).

Distribute pencils and paper clips to each pair of student to use as spinners in the activities for the My Day Activity Sheet and Class Schedule Activity Sheet (the spinners are located at the bottom of each activity sheet). To use the spinner, straighten out one fold in the paper clip. Place the pencil inside the loop in the paper clip and place the point of the pencil at the center of the spinner. Students will flick the paper clip, and the unfolded part will determine which section is selected. Before beginning the activity sheet, tell the students that if they spin the same class more than once, they can choose to re-spin or repeat the class. Also, emphasize that their schedules in these activities may not be realistic. For example, students will probably not spend 55 minutes in school, eat lunch at the beginning of the day, or spend 3 hours riding the bus home. This should be a fun activity in which students simply get to practice applying elapsed time. As students complete the activity sheets, circulate throughout the room to ensure that students are measuring and applying elapsed time correctly. Students will have different answers on My Day and Class Schedule, depending on their spins. You may choose to facilitate a discussion by asking students for some of their most interesting results. Some students will have very short or very long school days, sleep times, etc. After students have completed all the activities, have students note the end time.

To conclude the class, ask students to calculate how much time it took them to complete all the activities (use the time written on the board as a reminder for students). You can choose to discuss how they determined the elapsed time as a class, or you can collect these their answers on small index cards as a form of assessment.

Ideas for Differentiation

Lower-achieving students could be given spinners with smaller amounts of time, or use larger intervals of time. For example, some of the times for the Circus Manager Activity Sheet could be in half-hour increments.These students may also benefit from a shorter list of activities.

Assessment Options

1. Use guided questions throughout the independent portion of the lesson to determine mastery. Ask, "How long is it until lunch/PE/Math/etc.? How long did you spend on your homework? How long does it take you to walk to school, the park, etc.? How do you know? How did you figure it out?"
2. Have students design their own activity and spinner with a blank activity sheet and check to see that the times are calculated correctly. Students might also trade activities and spinners with a partner to provide more opportunities to practice.
3. Ask students to take a blank activity sheet and record on it how they spent a weekend day. Have them sum up the times for each entry.

Extensions

1. Students can also change their spinners to larger amounts of time, including hours greater than 24. For example, one of the spins could be 32 hours, 2 minutes, so these students will need to calculate the days in addition to the time.
2. Have the students do one of the activities by starting at the end of the day and working backwards. This way, students will need to subtract the time to find the start time for each activity. Students should be able to subtract along the timeline using the same techniques. Ask students when this would be a helpful way to determine elapsed time.

Questions for Students

1. How is measuring elapsed time different on the timeline compared to the analog clock?

[Answers might include that the clock hands rotate within the same circle so it can be challenging to keep track of the hours, but the timeline uses a linear measurement.]

2. Could you find elapsed time by counting backwards, from finish to start?

[Yes. The "distance" between the start and finish time is the same regardless of the direction you move in.]

3. Both a stopwatch and a timer measure elapsed time. Can you give an example when you would use each of them?

[Answers will vary. Sample answer: A stopwatch could be used to figure out how long it takes you to run a mile. A timer is useful when boiling an egg.]

Teacher Reflection

• How did you challenge all students at their level? Would more differentiation be helpful?
• How did your students demonstrate understanding of their work with elapsed time?
• What were some of the ways the students showed that they were actively engaged in the learning process?
• Did you find it necessary to make adjustments while teaching the lesson? If so, what types of adjustments were made, and were they effective?
• What other strategies and/or tools can I use with students to strengthen their understanding and fluency with this concept?

Learning Objectives

Students will:

• Use a timeline to measure elapsed time.

NCTM Standards and Expectations

• Develop fluency in adding, subtracting, multiplying, and dividing whole numbers.
• Develop and use strategies to estimate the results of whole-number computations and to judge the reasonableness of such results.
• Select and apply techniques and tools to accurately find length, area, volume, and angle measures to appropriate levels of precision.

Common Core State Standards – Mathematics

• CCSS.Math.Content.3.MD.A.1
Tell and write time to the nearest minute and measure time intervals in minutes. Solve word problems involving addition and subtraction of time intervals in minutes, e.g., by representing the problem on a number line diagram.