A circular ring has an inner radius of 10 cm and a wall thickness of 1 cm. What is the area of the ring in square centimetres?
一个圆环，内半径是10厘米，管壁厚度是1厘米，这个环形的面积是多少平方厘米．
<gadget id="calculator">10 + 1</gadget>
<output>11</output>

<gadget id="calculator">11 ** 2</gadget>
<output>121</output>

<gadget id="calculator">3.14 * 121</gadget>
<output>379.94</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100</gadget>
<output>314</output>

<gadget id="calculator">379.94 - 314</gadget>
<output>65.94</output>

<result>65.94</result>