The radius of a circle is 1 meter, if the radius is doubled, how many times will the circumference be enlarged.
圆的半径是1米，半径扩大2倍，周长扩大多少倍．
<gadget id="calculator">2 * 3.14 * 2</gadget>
<output>12.56</output>

<gadget id="calculator">2 * 3.14 * 1</gadget>
<output>6.28</output>

<gadget id="calculator">12.56 / 6.28</gadget>
<output>2</output>

<result>2</result>