If the radius of a circle is changed from 3 cm to 5 cm, how much does the area of the circle increase in square centimeters?
一个圆的半径由3厘米变成5厘米，圆的面积增加了多少Ⅱ平方厘米．
<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">25 - 9</gadget>
<output>16</output>

<result>16</result>