A trapezoid with an area of 40 square centimeters has a height of 8 centimeters, an upper base of 3 centimeters, and a lower base of 3 centimeters.
一个面积是40平方厘米的梯形，高是8厘米，上底是3厘米，下底是多少厘米．
<gadget id="calculator">2 / 8</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">40 * (1/4)</gadget>
<output>10</output>

<gadget id="calculator">10 - 3</gadget>
<output>7</output>

<result>7</result>