Unit Conversions

Lesson 8

Objective

Express time measurements in terms of a smaller unit, recording measurement equivalents in a two-column table. Solve one-step word problems that require time unit conversion.

Materials and Resources

Common Core Standards

Core Standards

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  • 4.MD.A.1 — Know relative sizes of measurement units within one system of units including km, m, cm; kg, g; lb, oz.; l, ml; hr, min, sec. Within a single system of measurement, express measurements in a larger unit in terms of a smaller unit. Record measurement equivalents in a two column table. For example, know that 1 ft is 12 times as long as 1 in. Express the length of a 4 ft snake as 48 in. Generate a conversion table for feet and inches listing the number pairs (1, 12), (2, 24), (3, 36), …

  • 4.MD.A.2 — Use the four operations to solve word problems involving distances, intervals of time, liquid volumes, masses of objects, and money, including problems involving simple fractions or decimals, and problems that require expressing measurements given in a larger unit in terms of a smaller unit. Represent measurement quantities using diagrams such as number line diagrams that feature a measurement scale.

Foundational Standards

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  • 3.MD.A.1

  • 4.OA.A.1

Criteria for Success

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  1.  Establish benchmarks for the units of a day, an hour, a minute, and a second. 
  2. Understand that a day is 24 times longer than an hour, an hour is 60 times longer than a minute, and a minute is 60 times longer than a second. 
  3. Use these relationships to convert measurements from a larger time unit to a smaller unit (MP.7, MP.8).
  4. Use these relationships to convert measurements from mixed time units to a smaller unit (MP.7, MP.8).
  5. Solve one-step word problems that require time unit conversions, including problems that involve elapsed time (MP.4).

Tips for Teachers

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Students have done extensive work with the relationships of time (2.MD.7a), how to read an analog clock (1.MD.3, 2.MD.7, 3.MD.1), and elapsed time (3.MD.1) in previous grades. Note, however, that 2.MD.7a is a Massachusetts-specific standard, but students are likely to know the relationships of time from real-world experience on their own.

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Anchor Tasks

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Problem 1

a. How many seconds are in a minute?

b. How many minutes are in an hour?

c. How many hours are in a day?

d. How are each of these relationships represented on an analog clock? A picture of one is shown below. 

Guiding Questions

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Problem 2

Fill in the following converstion tables.

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Problem 3

Anne, Matt, Cara, and Ross ran a half marathon but had staggered starts, so they aren’t sure who had the best time. They each recorded their run times in the following way:

Person Time
Anne 108 minutes 38 seconds
Matt 2 hours 4 seconds
Cara 6,873 seconds
Ross 2 hours 4 minutes

 

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Problem 4

United Airlines has the following contest:

You have the following flight information:

Leave

Wed, April 22

 

10:28 AM

San Fransisco

SFO

12:47 PM

Honolulu

HNL

non-stop

5 hr 19 min

total time

What would you submit as your contest entry?

Guiding Questions

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References

101Questions Halfway to Hawaii

Halfway to Hawaii by Dan Meyer is made available on 101Questions under the CC BY 3.0 license. Accessed June 29, 2018, 11:47 a.m..

Modified by The Match Foundation, Inc.

Discussion of Problem Set

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  • Look at #2(g) and #2(h). How many minutes are in a day? How many seconds are in a minute? How did you figure that out? 
  • What time did Juan arrive at his grandmother’s house in #8? How did you figure that out? 
  • How many minutes does Mr. Wilm stay at school in #10? How did you figure that out? 
  • Can anyone describe how time is kept in the military or in a foreign country? 
  • Is time (seconds, minutes, hours) defined as a metric or customary system?

Target Task

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Problem 1

Solve. 

a. 7 days = ____________ hours

b. 12 minutes 34 seconds = ____________ seconds

Problem 2

Jacob needs to do his chores. It takes Jacob an hour and 45 minutes to mow the lawn and 20 minutes to clean his room. If he starts his chores at 2:00 PM, what time will he finish?

Mastery Response

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