A dog breeder has 10 meters of
fencing with which to build a rectangular dog pen.

What
values of width and length (in meters) will enclose the largest area?

Below
the red rectangle represents the floor of the dog pen. Use your mouse to "drag"

the labeled
point to experiment with different widths. The blue curve represents the graph of
the area of the rectangle as a function of its width.

- Notice how the length changes.
- Notice that the perimeter is constant.
- Use the graph to approximate the value of the width that yields the
largest area.

This is a prototype of **JavaSketchpad**, a World-Wide-Web component of *The Geometer's Sketchpad.* Copyright ©1990-1998 by Key Curriculum Press, Inc. All rights reserved. Portions of this work were funded by the National Science Foundation (awards DMI 9561674 & 9623018).