Area and Perimeter of Triangles: Triangles Inside and Out

This is one lesson in a larger Unit Plan that covers many properties of triangles and several other theorems.  It has proofs, real world problems, constructions, a unit project, assessments, and more.  In Lesson 7, “Triangles Inside and Out (Area and Perimeter of Triangles)”, students investigate the relationship between triangle perimeter and area, and includes real world connections.  The entire unit plan can be found hereThis lesson includes the use of an applet that allows for manipulation of a triangle on a computer. This could be used individually in the computer lab, or in a group setting on an interactive board.

Standards & Objectives

Essential and guiding questions: 
  • How do area and perimeter compare and contrast?
  • How are area and perimeter related to other geometric topics?

Lesson Variations

Blooms taxonomy level: 

Helpful Hints


  • Worksheets
  • calculator
  • computer with internet access
  • dot paper
  • geoboards