If the inner radius of a ring is 3 cm and the width of the ring is 2 cm, what is the area of the ring in square centimetres?
一个圆环的内圆半径是3厘米，环宽是2厘米，则圆环的面积是多少平方厘米．
<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<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>