A circular iron sheet, the ratio of the inner diameter to the outer diameter is 3:5, the inner diameter is 6dm, find the area of this annular iron sheet.
一块环形铁皮，内圆直径和外圆直径的比是3：5，内圆直径是6dm，求这块环形铁皮的面积．
<gadget id="calculator">6 / 3</gadget>
<output>2</output>

<gadget id="calculator">2 * 5</gadget>
<output>10</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

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

<gadget id="calculator">6 / 2</gadget>
<output>3</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>