A circular flower garden is 180 meters long. If a willow tree is planted every 6 meters along the periphery of the flower garden, and a poplar tree is planted between every two willow trees, how many poplar trees can be planted?
一个圆形的花圃，绕一圈是180米．如果沿着花圃周围每隔6米种一棵柳树，每两棵柳树之间种一棵杨树，可种多少棵杨树．
<gadget id="calculator">180 / 6</gadget>
<output>30</output>

<result>30</result>