circle is formed with a piece of iron wire 7.71 meters long, leaving 3 meters at the joint. What is the radius of the circle?
用7.71米长的一条铁丝围成一个圆圈，接头处留出3米，圆圈的半径是多少？
<gadget id="calculator">7.71 - 3</gadget>
<output>4.71</output>

<gadget id="calculator">4.71 / 3.14 / 2</gadget>
<output>0.75</output>

<result>0.75</result>