Question

A passenger train left Austin, Texas at 12:00 PM bound for Dallas, exactly 210 miles away; it traveled at a steady 50 miles per hour. At the same time, a freight train left from Dallas headed for Austin at a steady 20 miles per hour. At the same time a fly leaped from the nose of the passenger train and flew along the track at 100 miles per hour. When the fly touched the nose of the oncoming freight train, she turned around and flew back at 100 miles per hour, when she reached the nose of the passenger train, she instantly turned and flew back toward the freight train. She continued turning and flying until the trains collided.1. After how long did the trains collide?2. How long before the fly reached the oncoming freight train?3. How far had the fly flown before the trains collided?

Answer 1

Answer:

1. 3 hours
2. 1 hour 45 minutes
3. 300 miles

Step-by-step explanation:

1. The trains are moving toward each other at a total speed of 50 +20 = 70 miles per hour. Together, they cover the 210 mile distance in ...

  time = distance/speed

  time = 210 mi/(70 mi/h) = 3 h

The trains collide after 3 hours.

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2. The fly is closing with the freight train at a speed of 100 +20 = 120 miles per hour. Together, the fly and the train cover the initial 210 mile distance in ...

  (210 mi)/(120 mi/h) = 7/4 h = 1 hour 45 minutes

The fly first meets the oncoming freight train after 1 h 45 min.

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3. The fly is flying for all three hours before the trains collide, so, at 100 miles per hour, will fly 300 miles.