Naughty measured the radius of the bottom of a can. He rolled the side of the can on the table and walked a total of 15.7 cm. What is the approximate radius of the bottom of the can?
淘气测量一个易拉罐底的半径，他把易拉罐的侧面放在桌子上滚了一圈，共走了15.7厘米．易拉罐罐底的半径大约是多少厘米？
<gadget id="calculator">15.7 / 3.14 / 2</gadget>
<output>2.5</output>

<result>2.5</result>