An iron ring rolls a circle and advances 1.57 meters, what is the radius of the iron ring in meters?
一个铁环滚动一周前进了1.57米，这个铁环的半径是多少米．
<gadget id="calculator">1.57 / 3.14 / 2</gadget>
<output>0.25</output>

<result>0.25</result>