Cut out the largest circle from a square of cardboard with a side length of 10 cm. What is the area of this circle in square centimeters?
从边长10厘米的正方形纸板上剪一个最大的圆，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>