GMAT 数学提问？

mandying

哪位高手帮在下解解这道题~~感觉题目有问题？？

A hiker walking at contant rate of 4 miles per hour is passed by a cyclist travelling in the same direction along the same path at a contant rate of 20 miles per hour, a cyclist stop to wait for the hiker 5 minutes after passing her, while the hiker continues to walk at her constant rate, how many minutes must the cyclist wait until the hiker catches up ?

答案是20minus~~~

mandying

 thanks so much~~ got it^.^

funnytigers

hiker: 4miles/hour=(4/60)miles/minute,
cyclist: 20miles/hour=(20/60)miles/minute,
cyclist在经过了hiker5分钟以后停下来等她
在这5分钟里：
cyclist走了(20/60)*5=(100/60)miles
hiker走了(4/60)*5=(20/60)miles
5分钟之后，在cyclist停下来等hiker的时候：
hiker和cyclist之间的距离是(100/60)miles-(20/60)miles=(80/60)miles
(80/60)miles除以hiker的速度(4/60)miles/minute，就得出cyclist需要等待的分钟数，也就是hiker赶上cyclist的时间，20minutes