# Where Has the Time Gone?

## Elapsed Time

K20 Center, Alexandra Parsons | Published: September 16th, 2020 by Oklahoma Young Scholars/Javits

• Subject Mathematics
• Course
• Time Frame 1-2 class period(s)
• Duration 90 minutes

### Summary

In this lesson, students investigate how to determine how much time has passed (by five-minute intervals). Prerequisites for this lesson are knowledge that time passes, that a clock measures time, and how to read a clock by five-minute intervals. Skip counting by fives is also needed for this lesson.

### Essential Question(s)

What are ways in which we can observe our world?

### Snapshot

Engage

Students will activate prior knowledge of number lines and clocks.

Explore

Students will use a number line or clock to figure out situations using time.

Explain

Students will walk through how to solve elapsed time problems.

Extend

Students will figure out how much time is spent learning during the day.

Evaluate

Students will create an elapsed time problem.

### Materials

• Number lines that include numbers 0-60, counting by fives (one for each student plus a larger version for the teacher)

• Student gear clocks (one for each student and one large Judy clock for the teacher)

• Elapsed Time Word Problems half page (one per student)

• Class schedule (one small copy for each student)

### Engage

Pass out a counting by fives number line to each student. If you have a class set of student gear clocks, pass those out to each student as well.

Ask students to Tell Me Everything about what the number line would be used for and what the clocks would be used for. For time's sake, you can allow this activity to be a whole group brainstorm.

### Explore

Hand out a copy of the Elapsed Time Word Problems to each student.

Start by reading the problems aloud or having students read the problems to themselves.

Ask students, "How can you use your clock to answer the first question?" Give them time (independently or in pairs) to think about it and try it out on their own.

Ask students "How can you use the number line or the clock to answer the questions?" Allow them time to think through the question and try to answer it on their own.

### Explain

After enough students have shared, grab your big teacher Judy clock.

Reread the first problem. Ask your students what time to start with on the clock. Once they answer, move your clock to 1:20. Ask students what time the problem ends. Put a sticky note or some other kind of marker at 2:00. Walk the students through how to use the clock to skip count by fives until the clock reads 2:00. When that's done, have the students write down the correct answer if they haven't already.

Get out a large number line marked by 5's. (For ease of concreteness, it should stop at 60.) Tell students that they can use the number line to solve the problem, too! Start at 20 on the number line and skip count by fives until you get to 60.

Reread the second problem. Go through the steps of modeling the problem on the clock just like you did with the first problem. Then, model the problem using the number line as before.

Repeat with the third problem as you've already done.

### Extend

Distribute a personal classroom schedule to each student.

Allowing for whichever method feels best for each student (number line, clock, etc.), ask students to determine how much time elapses for each part of their day.

### Evaluate

In their interactive notebooks, or on a piece of paper, have students Create the Problem. Ask them to think about things that they do in their life and write a problem similar to the problems they've worked on. When they're done have them switch with a partner and try to solve the problem using whichever method they prefer.