The outer diameter of a circular iron plate is 10 decimeters and the inner diameter is 6 decimeters. What is the area of the annular iron plate in square decimeters?
一个环形铁片的外圆直径是10分米，内圆直径是6分米，这个环形铁片的面积是多少平方分米．
<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>