A circular part has an outer radius of 5 cm and an inner radius of 3 cm, what is its area in square centimetres?
一个环形零件，外圆半径是5厘米，内圆半径是3厘米，它的面积是多少平方厘米
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">25 - 9</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</output>

<result>50.24</result>