爸爸驾车带着小青行驶在从甲地开往乙地的公路上。小青发现，路上每隔一段距离就有一个路灯，于是她数了数每分钟经过的路灯的数目，并告诉了爸爸。爸爸想了一下说：“真有意思，把这个数目乘５，正好等于我们的车速度。”（汽车的时速单位是“千米／小时”）。

如果爸爸的车速不变，且相邻两个路灯间的距离相等，那么，相邻两个路灯间的距离是多少？

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