The perimeter of a rectangle

Follow the description and watch the results! Try to solve the tasks beneath the applet.
Use the slider to move the point slowly up and down. Look what happens! Repeat the procedure with each point.

In the task above you can see a paled property. What do you think is meant by "the perimeter"?

Kreuze deine Antwort hier an
Use your notebook: Draw a regtangle with the length a und the width b. Write down the three formulas for the perimeter you have discovered.

Explain in your own words why we can use the formula for calculating the perimeter of a rectangle.