Convert a circle into an approximate rectangle. The perimeter of the converted rectangle is 10 cm longer than the circle. What is the area of the circle in square centimeters?
把一个圆转化成一个近似的长方形，转化后的长方形的周长比圆多10厘米，求这个圆的面积是多少平方厘米？
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

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

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<result>78.5</result>