The area of a trapezoidal iron sheet is 16dm**2, its height is 4dm, its upper base is 5.5dm, what is its lower base?
一块梯形铁皮的面积是16dm**2，它的高是4dm，上底是5.5dm，下底是多少？
<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">16 * (1/2)</gadget>
<output>8</output>

<gadget id="calculator">8 - 5.5</gadget>
<output>2.5</output>

<result>2.5</result>