The radius of a circle is 3 cm, if its radius is extended by 2 cm, how much will the area increase?
一个圆的半径是3厘米，如果把它的半径延长2厘米，那么面积增加多少．
<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<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>