Divide a circle into 64 parts and convert it into an approximate rectangle. If the perimeter of the rectangle is 10 cm longer than the perimeter of the circle, what is the area of the original circle?
把一个圆平均分成64份，转化成一个近似的长方形．如果长方形的周长比圆的周长大10厘米，那么原来圆的面积是多少．
<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>