What is the area of a roughly trapezoidal flower bed with a height of 10 meters and a sum of upper and lower bases of 16 meters?
一个近似梯形的花坛，高10米，上下底之和是16米，面积是多少．
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">16 * 5</gadget>
<output>80</output>

<result>80</result>