The sum of the upper and lower bases of a trapezoid is 2 meters and the height is 5 decimeters. What is its area?
一个梯形的上底和下底和是2米，高5分米，它的面积是多少．
<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">20 * (5/2)</gadget>
<output>50</output>

<result>50</result>