In order to protect an old tree, a 30-meter-long circular fence should be built for it in the garden. If a pile is driven every 2 meters, how many piles need to be driven in total?
为了保护一棵古树，园林处要为它做一个长30米的圆形防护栏．如果每隔2米打一个桩，一共需要打多少个桩？
<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<result>15</result>