The perimeter of a rectangular piece of land is 90 meters, and the ratio of length to width is 5:4. What is its area?
一块长方形地的周长是90米，长和宽的比是5：4，它的面积多少？
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">90 / 2 / 9</gadget>
<output>5</output>

<gadget id="calculator">5 * 5 * 5 * 4</gadget>
<output>500</output>

<result>500</result>