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K–12 teaching and learning · from the UNC School of Education

In your shadow

http://illuminations.nctm.org/LessonDetail.aspx?ID=L515

A lesson plan for grades 7–8 Mathematics

Provider: National Council of Teachers of Mathematics


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Students extend their knowledge of proportions to solving problems dealing with similarity. They measure the heights and shadows of familiar objects and use indirect measurement to find the heights of things that are much bigger in size, such as a flagpole, a school building, or a tree. Illuminations provides and activity sheet and detailed instructions for completing the lesson.

Students will:

  • Find the heights of very tall objects by measuring shorter objects and their shadows.
  • Use similarity and indirect measurement.
  • Set up and solve proportions.

NCTM Standards and Expectations:

  • Recognize and apply geometric ideas and relationships in areas outside the mathematics classroom, such as art, science, and everyday life.
  • Solve problems involving scale factors, using ratio and proportion.
  • Understand both metric and customary systems of measurement.
  • Select and apply techniques and tools to accurately find length, area, volume, and angle measures to appropriate levels of precision.
  • Understand, select, and use units of appropriate size and type to measure angles, perimeter, area, surface area, and volume.

North Carolina Curriculum Alignment

Mathematics (2004)

Grade 7

  • Goal 2: Measurement - The learner will understand and use measurement involving two- and three-dimensional figures.
    • Objective 2.01: Draw objects to scale and use scale drawings to solve problems.

Grade 8

  • Goal 2: Measurement - The learner will understand and use measurement concepts.
    • Objective 2.01: Determine the effect on perimeter, area or volume when one or more dimensions of two- and three-dimensional figures are changed.
    • Objective 2.02: Apply and use concepts of indirect measurement.