Plant trees around a circular field with a diameter of 10 meters, and plant one tree every 1.57 meters. How many trees can be planted in total?
一个直径是10米的圆形场地周围栽树，每隔1.57米栽一棵，一共可以栽多少棵．
<gadget id="calculator">10 / 1.57</gadget>
<output>6.369427</output>

<gadget id="calculator">3.14 * 6.369427</gadget>
<output>20.000001</output>

<result>20.000001</result>