Plant trees beside a circular fish pond with an interval of 4 meters. If a total of 25 trees are planted. What is the circumference of the pond in meters.
在一个圆形鱼池边种树，间隔是4米，如果共种25棵树．鱼池的周长是多少米．
<gadget id="calculator">25 * 4</gadget>
<output>100</output>

<result>100</result>