The radius of a circle is 4 centimeters, if the diameter increases by 2 centimeters, how much does its area increase in square centimetres?
一个圆的半径是4厘米，如果直径增加2厘米，它的面积增加多少平方厘米．
<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">4 + 1</gadget>
<output>5</output>

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

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

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

<gadget id="calculator">3.14 * 9</gadget>
<output>28.26</output>

<result>28.26</result>