If the radius of the circle is increased from 6 cm to 9 cm, the area of the circle increases by π square centimeters
圆的半径由6厘米增加到9厘米，圆的面积就增加了多少π平方厘米
<gadget id="calculator">9 ** 2</gadget>
<output>81</output>

<gadget id="calculator">6 ** 2</gadget>
<output>36</output>

<gadget id="calculator">81 - 36</gadget>
<output>45</output>

<result>45</result>