1989 AHSME Problems/Problem 3

Let $x$ be the width of a rectangle so that the side of the square is $3x$ . Since $2(3x)+2(x)=24$ we have $x=3$ . Thus the area of the square is $(3\cdot3)^2=81$ . These problems are copyrighted © by the Mathematical Association of America, as part of the American Mathematics Competitions.