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Area of Triangles

3-5, 6-8
Math Content:

How Do You Find the Area of a Triangle? 

To find the area of a triangle, find a way to make it look like a shape for which you already know how to find the area. Try to make a parallelogram using a copy of the triangle.

Release: 2015Q2, Semantic Version: 4.2.0, Build Number: 911.6-r, Build Stamp:

The goal is to create a parallelogram by using a copy of any triangle.

  • Change the size and shape of triangle ABC by dragging points A, B, and C.
  • Click the Create Copy button to make a copy of the purple triangle. Translate the yellow copy using point C, and rotate it using point B'.
  • The Construct Parallelogram button will complete the problem for you.
  • The Show Dimensions button indicates the dimensions needed to find the area, and Show Area button will show the area of triangle ABC.
  • The Reset button will allow you to start over.

Use the Create Copy button to create a yellow copy of the purple triangle. Try to arrange the two triangles to form a parallelogram. If you need help, the Construct Parallelogram button will show one way of making a parallelogram. There are also two other ways—can you find them?

  • What measurements on the triangle do you need to make in order to find the area of a parallelogram?
  • What is the area of the triangle?

Area Tool

Use this tool to determine how the length of the base and the height of a triangle, parallelogram, or trapezoid can be used to determine its area.