The big rabbit and the second rabbit race against the tortoise. In order to reflect the spirit of fairness, the starting point A of the two rabbits is a distance behind the starting point B of the tortoise, and the three animals start at the same time. The big rabbit is faster, catch up with the tortoise first, when the big rabbit catches up with the tortoise. The second rabbit was still 30 kilometers behind them, and then the three animals continued to run forward. When the second rabbit caught up with the tortoise, the big rabbit had already surpassed them by 40 kilometers. Come", so the three animals returned to the starting point, but this time the second rabbit stood at point B, and the starting distance between the big rabbit and the tortoise remained unchanged. When catching up with the two rabbits, how many kilometers did the tortoise lag behind them?
大兔子和二兔子一起和乌龟赛跑，为了体现公平精神，两只兔子的出发点A落后乌龟的出发点B一段距离，三只动物同时出发．大兔子比较快，先追上乌龟，当大兔子追上乌龟的时候．二兔子还落后它们30千米，接着三种动物继续向前跑，当二兔子追上乌龟的时候，大兔子已经超过它们40千米了，二兔子看到心里不高兴了，说："重来"，于是三只动物回到出发点，但是这一次二兔子站到了B点，大兔子和乌龟的出发距离不变，如果三只动物的速度不变，还是同时向前出发，那么当大兔子追上二兔子的时候，乌龟落后它们多少千米．
<gadget id="calculator">30 * 12</gadget>
<output>360</output>

<result>360</result>