A fly is resting on the front of a train that is hurtling forward at 60 kilome-

Question

A fly is resting on the front of a train that is hurtling forward at 60 kilome- ters per hour. On the same track, 300 kilometers straight ahead, another train is hurtling towards the first train at 60 kilometers per hour. At that moment, when the trains are 300 km apart, the fly takes off at 90 km per hour. He continually flies back and forth between the trains, flying just above the track and instantaneously turning around when he reaches a train. What is the total distance traveled by the fly before the two trains crash together, squishing the fly between them in the process? Explain your answer. A fly is resting on the front of a train that is hurtling forward at 60 kilome- ters per hour. On the same track, 300 kilometers straight ahead, another train is hurtling towards the first train at 60 kilometers per hour. At that moment, when the trains are 300 km apart, the fly takes off at 90 km per hour. He continually flies back and forth between the trains, flying just above the track and instantaneously turning around when he reaches a train. What is the total distance traveled by the fly before the two trains crash together, squishing the fly between them in the process? Explain your answer. A fly is resting on the front of a train that is hurtling forward at 60 kilome- ters per hour. On the same track, 300 kilometers straight ahead, another train is hurtling towards the first train at 60 kilometers per hour. At that moment, when the trains are 300 km apart, the fly takes off at 90 km per hour. He continually flies back and forth between the trains, flying just above the track and instantaneously turning around when he reaches a train. What is the total distance traveled by the fly before the two trains crash together, squishing the fly between them in the process? Explain your answer.

Explanation / Answer

As it has been mentioned, the fly continually flies back and forth with no delay while turning back.

So we had the speed with which the fly would keep on flying until it gets killed. We will determine the time for which the fly travels using the time required for the trains to crash into each other and then use that time to find the distance covered by the fly.

For the trains travelling in opposite directions, the distance to be covered = 300 kms

So the time for collision = 300 / 120 = 2.5 hours

The distance the fly will cover in this time interval = Speed x Time = 90 x 2.5 = 225 Kms

NOTE: There is another way to solve this problem and that would be forming equations for the distance travelled in one to and fro motion of the fly. That leads to a geometric progression which yields the same result. However, that method is unnecessarily complex.

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