Math Is Fun Forum

tony123

Member

Registered: 2007-08-03

Posts: 230

Two men

Two men are walking towards each other along the side of a railway. A freight train overtakes one of them in 20 seconds, i.e., it takes 20 seconds for the train, engine to caboose, to pass him. Exactly 10 minutes after just reaching the first man, the train meets the other man coming in the opposite direction. The train passes this man in 18 seconds. How long after the train has passed the second man will the two men meet?

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Two men

Let u be the speed of the train, v be the speed of the first person, and w be the speed of the second person. Suppose L is the length of the train. Then

Let D be the distance between the train and the second person at the instant it has just overtaken the first person. Thus

[Dickinson]D\ =\ 600(u+w)[/Dickinson]

and the distance between the two persons at that moment is

After the train has passed the second person, the distance between the two persons is

Hence the time for the two persons to meet after the train has passed the second person is 5562 seconds (1 hour 32 minutes 42 seconds).