A circle has an inner radius of 3 decimeters and an outer radius of 5 decimeters. What is the area of the circle in square decimeters?
一个环形，内圆半径是3分米，外圆半径是5分米，这个环形的面积是多少平方分米？
<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>