If the radius of a circle is increased by 4 cm, how many cm does the circumference increase
圆的半径增加4厘米，周长增加多少厘米
<gadget id="calculator">2 + 4</gadget>
<output>6</output>

<gadget id="calculator">2 * 3.14 * 6</gadget>
<output>37.68</output>

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

<gadget id="calculator">37.68 - 12.56</gadget>
<output>25.12</output>

<result>25.12</result>