A horse travels a certain distance each day. Strangely enough， two of its legs travel 30 miles each day and the other two legs travel nearly 31 miles. It would seem that two of the horse’s legs must be one mile ahead of the other two legs， but of course this can’t be true. Since the horse is normal， how is this situation possible？
　　Answer：
　　The horse operates a mill and travels in a circular direction. The two outside legs will travel a greater distance than the two inside legs.
　　译文：
　　有一匹马每天都要跑一定距离的路程。十分奇怪的是，它有两条腿每天跑了30英里路，而另外两条腿则跑了近31英里路。这似乎表明：有两条马腿在另外两条马腿的前方1英里处。这匹马是普通的马，请问这种情况在何时才有可能发生呢？
　　
　　答案：
　　在马拉磨时发生。因为它是绕圈前进，所以外侧的两条腿总是比内侧的两条腿走得更远。

趣味英语：奇怪的马