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Solve Problems Involving Time (Part 1)

Grade 3: Unit 6: Lesson 10

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Let’s solve problems involving time.

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Choral Count: Fifteens

Warm-Up

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Choral Count: Fifteens

Count by fifteens starting at 12:00

What patterns do you see?

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Let’s Talk About It!

How much time passed between 1:15 and 1:45?” (30 minutes) “1:15 and 2:30?

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Time at the Bus Stop

Activity 1

5 Practices
MLR7: Compare and Connect

In this activity, students solve problems involving elapsed time in a way that makes sense to them.

Although the problem type may be new, students can reason about them using their understanding

of time and of addition and subtraction. They can also support their reasoning by drawing on a

clock.

In each problem, students are given a start time and an elapsed time of 24 minutes. To find each

end time, students may:

• use words to describe their thinking

• write a series of numbers and symbols to show how 24 minutes is added to the start time

• create a table to track changes in time from the start time to 24 minutes later

• show incremental “jumps” that add up to 24 minutes on the clock

• use a linear representation to show incremental changes from the start time to 24 minutes

later

To elicit and discuss as many possible strategies and representations for reasoning about the

problems, significant time is allocated for this activity. Students may choose to use any of the

strategies or representations they see here to solve elapsed time problems in future lessons.

When they determine what time different events occurred based on the initial time and the 24

minutes of elapsed time students reason abstractly and quantitatively(MP2).

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a. Kiran arrived at the bus stop at 3:27 p.m., as shown on this clock. He waited 24 minutes for his bus to arrive.

What time did his bus arrive? Show your thinking. Organize

it so it can be followed by others.

Launch

• Groups of 2

• “Have you ever ridden a bus? When or where?” (I ride a school bus to school. I ride the city bus

with my parents. I rode a bus at the airport to get to our car in the parking lot.)

• “What are some things you need to know about when you ride the bus?” (What time will the

bus come? How often does the bus come? Where does the bus pick you up? Where are you

getting off? How long will your bus ride take? How much does the bus cost?)

• 1–2 minutes: partner discussion

• Share and record responses.

Student Work Time

• “Now solve the problems about Kiran and Elena riding the bus. Show your thinking in any way

that makes sense to you.”

• 8–10 minutes: independent work time

• As students work, consider asking:

◦ “How does your work show the 24 minutes Kiran or Elena waited?”

◦ “How does your work show the time the bus arrived?”

◦ “How did you know it would be before or after 4:00 when the bus arrived?”

• Monitor for and identify students who use the strategies listed in the activity narrative.

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b. Elena arrived at the bus stop at 3:45 p.m. She also waited 24

minutes for her bus to arrive.

What time did the bus arrive? Show your thinking. Organize

it so it can be followed by others.

Launch

• Groups of 2

• “Have you ever ridden a bus? When or where?” (I ride a school bus to school. I ride the city bus

with my parents. I rode a bus at the airport to get to our car in the parking lot.)

• “What are some things you need to know about when you ride the bus?” (What time will the

bus come? How often does the bus come? Where does the bus pick you up? Where are you

getting off? How long will your bus ride take? How much does the bus cost?)

• 1–2 minutes: partner discussion

• Share and record responses.

Student Work Time

• “Now solve the problems about Kiran and Elena riding the bus. Show your thinking in any way

that makes sense to you.”

• 8–10 minutes: independent work time

• As students work, consider asking:

◦ “How does your work show the 24 minutes Kiran or Elena waited?”

◦ “How does your work show the time the bus arrived?”

◦ “How did you know it would be before or after 4:00 when the bus arrived?”

• Monitor for and identify students who use the strategies listed in the activity narrative.

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Let’s Talk About It!

In Elena’s problem, how does each of the strategies help us see that the bus would come after 4:00?

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Time on the Bus

Activity 2

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Here’s another problem about time:

At 6:32 p.m., Elena got on a bus to go home. She got off the bus at 7:10 p.m. How long was her bus ride?

Which strategy or representation would you use when solving a problem like this? Explain your reasoning.

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Lesson Synthesis

Today we solved problems about time. We saw that we could use many ways to reason about the solutions and different representations to show our thinking.
Which strategies would you want to keep in mind when you solve future problems about time?

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Soccer Time

Cool-Down

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Clare leaves school at 3:25 p.m. Her soccer practice begins at 4:15 p.m. How much time does she have to get to the soccer field?

Explain or show your reasoning.

Cool-Down: Soccer Time

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Image Citations

https://giphy.com/stickers/interior-home-decor-present-time-PBN6hNm4q6KabSJ2jX

https://media.giphy.com/media/xkSkJcR2GVN4cJvRSy/giphy.gif

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