The lower base of a trapezoid is 10 cm. If the upper base is extended by 4 cm, it becomes a parallelogram with an area increased by 10 cm2. What is the area of the original trapezoid?
一个梯形下底为10厘米，如果上底延长4厘米，它就变成一个平行四边形，面积增加了10平方厘米，原梯形面积为多少平方厘米？
<gadget id="calculator">10 - 4</gadget>
<output>6</output>

<gadget id="calculator">6 + 10</gadget>
<output>16</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">10 * (1/2)</gadget>
<output>5</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">16 * (5/2)</gadget>
<output>40</output>

<result>40</result>