The Cassette Recorder

A train moving at a speed of 49 mph is passed by a train moving at a speed 63 mph.

A passenger in the first train noted that the second train took 4.5 seconds to pass

him.

How long is the second train?

Ah! Click here to read the solution.

1. The relative velocity between the trains is 112 mph (63 + 49).

2. To get the answer we must multiply the velocity times the time.

3. To get the correct units, convert mph to feet per sec, then multiply times 4.5 sec to get the answer in feet.

Answer: (5289 x (49 + 63) x 4.5) / (60 x 60) = 740.46 feet.

The length of the second train is ‘740.46’ feet

Related Brain Teaser: