As you may recall, the perimeter of a figure is a measure of the distance around it (or the sum of all sides). If you know the lengths of two sides of an object that is rectangular or if you know the length of one side of an object that is a square, you can find the perimeter without measuring the lengths of all sides. It is even possible to find the perimeter, or an expression that represents the perimeter, of such figures when you don't know the lengths of the sides.The application illustrates such a situation.

The interactive application shows how to find the perimeter of a rectangular object, given algebraic expressions that represent the lengths of two sides of the object. Try finding the expressions that represent the perimeter using paper and pencil first. Then use the interactive application to check your work. To use the application, click on the "play" button and then enter the appropriate values into the boxes. For expressions containing subtraction signs, you must rewrite the expression using an addition sign and a negative sign before you can enter the expression into the application. (For example, 2x - 1 must be rewritten as 2x + -1.) You may have to hit the "enter" key after entering new values in order to refresh the application.