For a right-angled trapezoid, if the upper base is extended by 10 cm, the area will increase by 200 cm2 and become a square. What is the area of the original trapezoid in square centimeters?
一个直角梯形，如果把上底延长10厘米，面积就增加200平方厘米，并且变成了一个正方形．原来梯形的面积是多少平方厘米．
<gadget id="calculator">2 / 10</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">200 * (1/5)</gadget>
<output>40</output>

<gadget id="calculator">40 * 40</gadget>
<output>1_600</output>

<gadget id="calculator">1_600 - 200</gadget>
<output>1_400</output>

<result>1_400</result>