The area of a trapezoid is 64dm**2, the height is 4dm, the upper base is 4dm, what is the lower base.
一个梯形的面积是64dm**2，高是4dm，上底是4dm，下底是多少．
<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">64 * (1/2)</gadget>
<output>32</output>

<gadget id="calculator">32 - 4</gadget>
<output>28</output>

<result>28</result>