A pot for ornamental bonsai is cylindrical. A ribbon is tied around the edge of the basin for decoration. It is known that the length of the ribbon is 3.012 meters, and 0.5 meters is used for the knotted shape. What is the radius of the base of this bonsai?
一个观赏盆景的花盆是圆柱形的．盆沿处捆一条丝带做装饰，已知丝带的长为3.012米，打结造型处用去0.5米．这个盆景的底面半径是多少米？
<gadget id="calculator">3.012 - 0.5</gadget>
<output>2.512</output>

<gadget id="calculator">2.512 / 3.14 / 2</gadget>
<output>0.4</output>

<result>0.4</result>