# Activities

• • • ##### Subject Area

• Math: Algebra II: Equations
• Math: Algebra II: Radical Functions
• Math: Algebra II: Rational Expressions

• ##### Author 9-12

45 Minutes

• ##### Device
• TI-83 Plus Family
• TI-84 Plus
• TI-84 Plus Silver Edition

TI Connect™

• ##### Accessories

TI Connectivity Cable

• ##### Report an Issue

Living on the Edge #### Activity Overview

Students find the edge length of an octahedron when given its volume.

#### Key Steps

• Students build a solution to a rather complex problem—finding the edge length of an octahedron given its volume—by solving two simpler problems.

First, students find a formula for the edge length of a square given its area.

• After testing this formula by comparing points on its graph with the measurements of a model square, they write an equivalent formula with fractional exponents and substitute values to find the edge length of a particular square. Students will repeat this process for the formula for the edge length of a cube given its volume.

• Finally, students solve an equation involving several different radical expressions to find a formula for the edge length of an octahedron given its volume, and use it to solve the original problem.