Quiz when eating moon cake

Reading Time: < 1 minute Copied from Zhuping’s blog: 一次,诺贝尔经济学获奖者数学家约翰·纳什参加一个数学年会,会间休息的时候,有人就给他出了一道数学题。有甲、乙两人分别从两个地点出发往中间走,这两个地点相距 20公里,甲、乙两人的速度都是每小时10公里。甲还带了一条狗,这条狗的速度是每小时30公里,它先是和甲一起出发向乙走,遇到乙后就折返向甲走,遇到甲后再折返向乙走,如此反复直到甲、乙在中间会合。现在问当甲、乙在中间会和时,狗走了多远。 Two people (guy A and guy B), who are 20 km away from each other, are walking toward each other, at 10 km per hour. There is a dog, which goes at 30 km per hour. She (the dog) started with the guy A first. Because she goes faster… Continue reading Quiz when eating moon cake