If the circumference of a circle is 15.7cm, what is the radius of the circle (take 3.14 for π).
圆的周长是15.7cm，则圆的半径是多少(π取3.14)．
<gadget id="calculator">2 * 3.14</gadget>
<output>6.28</output>

<gadget id="calculator">15.7 / 6.28</gadget>
<output>2.5</output>

<result>2.5</result>