Maths: Flying train

[TheGuru]

TheGuru will give 100 of his tokens to the first person to post the correct answer to the puzzle below

Two trains are are 200 miles apart and are running on same track towards each other. One is travelling at 40mph, the other at 60mph. In between the two trains there is a fly travelling at 65mph. It first flies in one direction and finds there is a train coming towards it. It changes its direction and flies towards the other train. As it reaches the other train it changes direction and goes back again. In this way, the fly keeps oscillating between the two trains.

How much distance does the fly cover before the trains crash and crush it?

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Hi Guru,

I think I have solved the problem

The fly will have covered 130 miles.

Why?

The movement of the first train can be described by the equation s=40*t
The movement of the second train can be described by the equation s=200-60*t (it starts 200 miles away and runs in the opposite direction)
The two trains will crush when 40*t=200-60*t, that is t=200/100=2 hours
Meanwhile, the fly will have covered s=65*t=65*2=130 miles

Is it OK :?:

JC

[TheGuru]

Correct, another 100 tokens are on the way to you


The Guru