The sum of the upper and lower bases of a trapezoid is 20m, the height is 5m, what is the area?
一个梯形的上底与下底的和是20m，高是5m，面积是多少．
<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>