Curriculum  /  Math  /  3rd Grade  /  Unit 7: Measurement  /  Lesson 5

Measurement

Lesson 5

Math

Unit 7

3rd Grade

Lesson 5 of 12

Objective

Solve word problems involving elapsed time that involves crossing the hour mark.

Common Core Standards

Core Standards

  • 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.

Criteria for Success

  1. Solve word problems involving addition and subtraction of time intervals in minutes, e.g., by representing the problem on a number line diagram, where the times cross the hour mark, including the following three cases:
    1. Where the end time is unknown, 
    2. Where the start time is unknown, and 
    3. Where the duration is unknown (MP.1, MP.4).

Tips for Teachers

  • According to 3.MD.1, students are expected to "solve word problems involving addition and subtraction of time intervals in minutes." Bill McCallum notes on his blog, "'Time intervals in minutes' doesn’t have to mean 'less than an hour.' For example, there’s no reason why Grade 3 students can’t say how many minutes it is from 3:30 to 5:00" (Elapsed Time (3.MD.1 vs. 4.MD.2), Mathematical Musings). Thus, the Problem Set and Extra Practice Problems include problems where students will work with elapsed time that is still given in minutes, as the standard requires, but exceeds an hour.
  • As noted in Lesson 4, “an open number line can be a useful tool to help students visualize and organize the information” given in elapsed time problems and find their solution" ("Dajuana's Homework", Illustrative Mathematics).
  • No matter what, avoid having students try to solve these problems as they would typical addition and subtraction problems, since base 60 (as is the case with minutes and hours) is very challenging to compute in. For example, students should not find the amount of elapsed time between 4:30 p.m. and 5:13 p.m. by regrouping an hour to be 4:73 and subtracting. 
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Anchor Tasks

25-30 minutes

Problem 1

a.   It usually takes Dajuana 45 minutes to do her homework. If she starts her homework at 5:30 p.m., what time will she finish?

b.   On the weekend, Dajuana started her homework at 11:45 a.m. and finished her homework at 12:20 p.m. How long did Dajuana spend on her homework?

c.   Another day, Dajuana finished her homework at 5:05 p.m. after spending 40 minutes on her homework. What time did Dajuana start her homework?

Guiding Questions

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Student Response

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References

Illustrative Mathematics Dajuana's Homework

Dajuana's Homework, accessed on March 28, 2019, 4:57 p.m., is licensed by Illustrative Mathematics under either the CC BY 4.0 or CC BY-NC-SA 4.0. For further information, contact Illustrative Mathematics.

Modified by Fishtank Learning, Inc.

Problem 2

a.   Ms. Banta leaves school at 4:52 p.m. She gets home at 5:13 p.m. How long was Ms. Banta’s commute home?

b.   Katherine wakes up from a nap at 2:26 p.m. Her watch tells her that she slept for 43 minutes. What time did Katherine fall asleep?

c.   On New Year’s Eve, Fernando’s parents wake him up so that he can watch the ball drop. He wakes up at 11:48 p.m. He’s up for 19 minutes before going back to bed. What time did Fernando go back to bed?

Guiding Questions

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Student Response

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Problem Set

15-20 minutes

Discussion of Problem Set

  • How did you solve #1? Did you use the clock, draw a number line, or use some other strategy? 
  • Did you count forward or backward to solve #3? How did you decide which strategy to use? 
  • What made #6 and #8 slightly more difficult than the other problems? Did you solve them differently? 
  • How did we use counting as a strategy to problem solve today? 
  • How did you use hour benchmarks to problem solve today? 

Target Task

5-10 minutes

Minna’s soccer practice ends at the time shown on the clock below. Practice was 55 minutes long. At what time did Minna’s soccer practice start?  

Student Response

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Additional Practice

The Extra Practice Problems can be used as additional practice for homework, during an intervention block, etc. Daily Word Problems and Fluency Activities are aligned to the content of the unit but not necessarily to the lesson objective, therefore feel free to use them anytime during your school day.

Word Problems and Fluency Activities

Word Problems and Fluency Activities

Help students strengthen their application and fluency skills with daily word problem practice and content-aligned fluency activities.

Next

Solve word problems involving all cases of elapsed time in minutes.

Lesson 6
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Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Time Measurement

Topic B: Mass and Liquid Volume Measurement

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