A circle has an outer radius of 6 cm and an inner radius of 5 cm, what is its area in square centimetres?
一个圆环，外圆半径是6厘米，内圆半径是5厘米，它的面积是多少平方厘米．
<gadget id="calculator">6 ** 2</gadget>
<output>36</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">36 - 25</gadget>
<output>11</output>

<gadget id="calculator">3.14 * 11</gadget>
<output>34.54</output>

<result>34.54</result>