For a trapezoid, the ratio of the upper base to the lower base is 4:9. If the lower base is reduced by 15 cm, it becomes a square. What is the area of the original trapezoid in square centimeters?
一个梯形，上底与下底的比是4：9，把下底减少15厘米，就变成一个正方形，原来梯形的面积是多少平方厘米？
<gadget id="calculator">4 + 9</gadget>
<output>13</output>

<gadget id="calculator">9 - 4</gadget>
<output>5</output>

<gadget id="calculator">15 / 5</gadget>
<output>3</output>

<gadget id="calculator">13 * 3</gadget>
<output>39</output>

<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">39 * 6</gadget>
<output>234</output>

<result>234</result>