Plant trees around a circular playground with a diameter of 40 meters, and plant one tree every 6.28 meters. How many trees can be planted in total?
在一块直径为40米的圆形操场周围栽树，每隔6.28米栽一棵，一共可栽多少棵？
<gadget id="calculator">3.14 / 6.28</gadget>
<output>0.5</output>

<gadget id="calculator">40 * 0.5</gadget>
<output>20</output>

<result>20</result>