If the radius of a circle increases by 3 centimeters, how many centimeters does the circumference increase?
一个圆的半径增加3厘米，周长增加多少厘米．
<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">2 * 3.14 * 5</gadget>
<output>31.4</output>

<gadget id="calculator">2 * 3.14 * 2</gadget>
<output>12.56</output>

<gadget id="calculator">31.4 - 12.56</gadget>
<output>18.84</output>

<result>18.84</result>