When the radius of a circle increases by how many centimeters, its circumference increases by 12.56 centimeters.
一个圆的半径增加多少厘米时，它的周长就增加12.56厘米．
<gadget id="calculator">12.56 / 3.14 / 2</gadget>
<output>2</output>

<result>2</result>