If the radius of a circle changes from 3 decimeters to 5 decimeters, how many square centimeters does the area of the circle increase?
一个圆的半径由3分米变成5分米，那么这个圆的面积增加了多少平方厘米？
<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>