Area of a Rhombus

Let half-diagonals be $3x$ and $4x$. Since diagonals bisect perpendicularly, $(3x)^2 + (4x)^2 = 15^2 \implies 25x^2 = 225 \implies x = 3$. Diagonals are $d_1 = 18$, $d_2 = 24$. Area = $\frac{1}{2} imes 18 imes 24 = 216\text{ cm}^2$. Since 216 is not in choices A-D, answer is E (None of the above).