Education Technology

Math TODAY: When a Ruler Isn't Enough

Activity Overview

Using the USA TODAY® Infograph, "When a Ruler Isn't Enough," you will explore the geometric relationships in similar right triangles. The altitude to the hypotenuse will create two right triangles that are similar to each other and to the original.
Students will determine measurements indirectly by using properties of similar triangles and apply the relationships to find solutions to a real world problem.

Before the Activity

Provide one graphing calculator for each student. Each student should have a copy of the corresponding student activity sheet. Provide each student with the following calculator file (AppVar) GEOMEAN.

During the Activity

  • Have the students link their calculator and share the AppVar as part of the class period on the previous day or during the beginning of the class period when you are going to use this activity. (Insure that graphing calculators have been updated with the latest version of operating system and Cabri Jr.)
  • Review opening an AppVars using Cabri Jr. with your class before starting the activity. Students can work individually or in groups to assist each other during the activity.
  • Have students discuss their discoveries while they work to better understand the relationships.
  • Before starting the AppVars, remind students to carefully read the opening screen and the activity pages.
  • Have students illustrate the geometric mean property with a diagram and summarize by using a proportion and a similarity statement.
  • After the Activity

  • Review student answers
  • As a class, discuss questions that appeared to be more challenging
  • Re-teach concepts as necessary