Education Technology

Follow the Fence, Then the Hypotenuse

Published on 06/09/2008

Activity Overview

In this activity, students use the Geoboard to determine the length of the hypotenuse of a right triangles.

Before the Activity

  • Start the Geoboard App and format it
  • See the attached PDF file for detailed instructions for this activity
  • Print pages 77 - 81 from the attached PDF file for your class
  • During the Activity

    Distribute the page to the class.

    Follow the Activity procedures:

  • Using vertical and horizontal sides, draw squares with areas of 1, 4, 9, and 25 square units
  • Find the length of the sides of the squares
  • Note that the length of sides is found by taking the square root of the area and area is found by squaring the side
  • Draw a rectangle to represent the pasture in the word problem and mark its diagonal
  • Note that the diagonal divides the rectangle into two congruent right triangles, and is called the hypotenuse
  • Draw a square in which the triangle's hypotenuse is the length of the square's side
  • Find the area of the square by surrounding it with a larger square and subtracting the four triangular corners
  • Calculate the area of the smaller square to be 25 square miles
  • If the area of the square built off of the hypotenuse is 25 square units, the diagonal is 5 miles


  • Draw the given triangle on the Geoboard, build a square on its hypotenuse, find the area of the square, and the measure of the triangle's hypotenuse
  • After the Activity

    Review student results:

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