Cut a largest circle on a square iron plate with a side length of 12 cm. What is the area cut off in square centimeters?
在一边长是12厘米的正方形铁片上，剪一个最大的圆，剪去的面积是多少平方厘米．
<gadget id="calculator">12 * 12</gadget>
<output>144</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">6 ** 2</gadget>
<output>36</output>

<gadget id="calculator">3.14 * 36</gadget>
<output>113.04</output>

<gadget id="calculator">144 - 113.04</gadget>
<output>30.96</output>

<result>30.96</result>