If the radius of a circle changes from 4 cm to 8 cm, how much does the area of the circle increase by π square centimeters?
圆的半径由4厘米变成8厘米，圆的面积增加了多少π平方厘米
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">64 - 16</gadget>
<output>48</output>

<result>48</result>