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Home | Lessons
Lesson 5: How Tall Is It?
Objectives:
Students will explore situations involving quantities that cannot be measured directly or conveniently.
Estimated Time of Completion:
One - two class periods.
Best Suited for 6th - 8th grade
Standards:
Understand measurable attributes of objects and the units, systems, and processes of measurement.
- Understand, select, and use units of appropriate size and type to measure angles, perimeter, area, surface area, and volume.
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Apply appropriate techniques, tools, and formulas to determine measurements.
- Select and apply techniques and tools to accurately find length, area, volume, and angle measures to appropriate levels of precision.
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NCTM Principles and Standards for School Mathematics page 240.
Supply List:
- String (optional)
- Pencil or stick
- Mirror
- "How Tall Is It?" handout (Download PDF)
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Procedure:
- As a whole class, read the handout, "How Tall Is It? The excerpts provide information about Lewis and Clark's techniques for measuring landmarks and other objects not easily measured. For photos and information on Beacon Rock visit:
vulcan.wr.usgs.gov/Volcanoes/Washington/BeaconRock/images.html
vulcan.wr.usgs.gov/Volcanoes/?Washington/BeaconRock/framework.html
www.inthegorge.com/beacon_rock.html
www.parks.wa.gov/parkpage.asp?selectedpark=Beacon+Rock
- Students will brainstorm ways to measure the height of something that isn't easily measured. Discuss when might a person need to know the height of something like this?
- Students will measure the height of a tall object such as a flagpole, tree, or large building in the neighborhood.
- Discuss possible strategies used for this activity.
- Students can use their knowledge of similar triangles to measure the height of inaccessible objects.
- Two possibilities are shown below, one using shadows and the other using reflections in a mirror. See the diagrams to teach specific methods that work.
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- Discuss how accurate are the measurements and when is close enough acceptable and when is it not appropriate. Have students defend their solution for accuracy.
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Assessment:
- To assess the level of student understanding ask these questions as you review their work.
- Were students able to choose a reasonable strategy to solve the problem?
- Were the students accurate in their calculations?
- What do students need to know to be able to reach a more reasonable solution?
- Were students able to communicate their thinking? Were they able to defend their solutions?
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Extension Ideas:
Brainstorm ways to measure the width of a river or other broad object that you cannot walk across. Set up a fake river or creek or use a real on in the neighborhood and ask students to estimate its width.
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