If the radius of a circle increases from 1 cm to 3 cm, its area increases by how many square centimeters.
一个圆的半径由1厘米增加到3厘米，它的面积增加了多少平方厘米．
<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">3.14 * 8</gadget>
<output>25.12</output>

<result>25.12</result>