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IGD: Area of a Parallelogram

3-5, 6-8
Math Content:

How Do You Find the Area of a Parallelogram?

In a parallelogram, opposite sides are parallel and have the same length. This applet will show you how to divide the parallelogram into pieces, arrange them together to form a rectangle, and then use the formula for the area of a rectangle to find the area of the parallelogram.

Sorry, this page requires a Java-compatible web browser.

Return to the IGD: Areas Overview.

  • Drag vertices A and B to change the size and shape of the parallelogram.
  • Drag the red point to move the right half of the parallelogram. Move this piece to create a rectangle with the left half. Click the Make Rectangle box to be shown how a rectangle can be made from the parallelogram.
  • Click the Show Dimensions button to indicate the measurements needed to find the area.
  • The Start Over button resets the diagram.

Change the size and shape of the parallelogram by dragging points A and B. Then, drag the right half of the parallelogram to form a rectangle with the left half.

  • What is the area of the rectangle that you get?
  • Click the Show Dimensions. What measurements of the parallelogram do you need in order to find its area?

Click the Start Over button, and repeat the investigation for parallelograms of other sizes.

  • Are your conjectures true, regardless of the size of the parallelogram?
  • Do all the parallelograms have the same area?

IGD: Area of a Rectangle

3-5, 6-8
Use this tool to show how the side lengths of a rectangle affect the rectangle's area.

IGD: Area of a Triangle

3-5, 6-8
Use this tool to prove how to find the area of a triangle.