The sum of the upper and lower bases of a trapezoid is 16dm, the height is 10dm, what is its area dm**2.
一个梯形上、下底之和是16dm，高是10dm，它的面积是多少dm**2．
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

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

<result>80</result>