The sum of the upper and lower bases of a trapezoid is 18 decimeters, and its area is 36 square decimeters. What is its height?
一个梯形的上底与下底的和是18分米，面积是36平方分米，它的高是多少．
<gadget id="calculator">2 / 18</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">36 * (1/9)</gadget>
<output>4</output>

<result>4</result>