For a right-angled trapezoid, if the upper base is extended by 5 cm, the area will increase by 25 cm2 and become a square. Find the area of the original rectangular trapezoid. (Hint: draw this right-angled trapezoid on the draft paper to help you understand the meaning of the question)
一个直角梯形，如果把上底延长5厘米，面积就增加25平方厘米，这时变成一个正方形．求原来直角梯形的面积．(提示：在草稿纸上画一画这个直角梯形，帮助你理解题意)
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">25 * (2/5)</gadget>
<output>10</output>

<gadget id="calculator">10 * 10</gadget>
<output>100</output>

<gadget id="calculator">100 - 25</gadget>
<output>75</output>

<result>75</result>