A trapezoid, the sum of the upper and lower bases is 9m, and the height is 5m, what is the area of the trapezoid?
一个梯形，上、下底的和是9m，高是5m，则这个梯形的面积是多少．
<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">9 * (5/2)</gadget>
<output>45/2 = around 22.5</output>

<result>45/2 = around 22.5</result>