For a parallelogram, if the height increases by 5 cm and the base remains the same, the area increases by 45 cm2; if the height remains the same and the base decreases by 5 cm, the area decreases by 30 cm2. What is the area of the original parallelogram in square centimeters?
一个平行四边形，若高增加5厘米，底不变，面积就增加45平方厘米；若高不变，底减少5厘米，面积就减少30平方厘米．原来平行四边形的面积是多少平方厘米？
<gadget id="calculator">45 / 5</gadget>
<output>9</output>

<gadget id="calculator">30 / 5</gadget>
<output>6</output>

<gadget id="calculator">9 * 6</gadget>
<output>54</output>

<result>54</result>