trapezoidal steel plate has an area of 580 square decimeters, an upper base of 18 decimeters, and a lower base of 40 decimeters. How many decimeters is the height?
一个梯形钢板，面积是580平方分米，上底是18分米，下底是40分米，高是多少分米？
<gadget id="calculator">2 / 58</gadget>
<output>1/29 = around 0.034483</output>

<gadget id="calculator">580 * (1/29)</gadget>
<output>20</output>

<result>20</result>