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jmc

algebra junior

Problem

The length of a rectangle is four times its width. The perimeter is 100 cm. What is the number of square centimeters in the area of the rectangle?
Solution
Let the length of the rectangle be and the width be . We are trying to find the area of the rectangle, or , so we need to first find both and . We can set up the following system of equations to represent the given information:



We will first solve for by eliminating from the equations above. Substituting the first equation into the second to eliminate , we get or . Plugging this value into the first equation gives . Thus, the area of the rectangle is square centimeters.
Final answer
400