The area of a trapezoid is 40 square meters, its upper base is 4 meters, and its height is 8 meters. What is its lower base in meters?
一个梯形的面积是40平方米，它的上底是4米，高是8米，它的下底是多少米．
<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 - 4</gadget>
<output>6</output>

<result>6</result>