The sum of the upper and lower bases of a trapezoid is 10 meters and the height is 20 meters. What is its area in square meters?
一个梯形上底与下底的和是10米，高是20米，它的面积是多少平方米．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 * 10</gadget>
<output>100</output>

<result>100</result>