The area of a square piece of paper is 100 square centimeters, and the largest circle is cut out of this paper, what is the area of the circle in square centimeters?
一张正方形纸的面积是100平方厘米，用这张纸剪成一个最大的圆，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>