What is the total distance that the supersonic bird has traveled till the trains collided?

Question

Accidentally, two trains are running in the opposite direction and enter a tunnel that is 200 kms long. A supersonic bird that has fled the lab and taken shelter in the tunnel starts flying from one train towards the other at a speed of 1000 kmph. As soon as it reaches the second train, he starts flying back to avoid collision and meets the first train again at the other end. The bird keeps flying to and fro till the trains collide with each other.

What is the total distance that the supersonic bird has traveled till the trains collided?

Comments

Please clarify, what is the speed of trains?

Answer 1

The distance = 5*(s1+s2), where s1&s2 are trains' speed in kmph

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Since trains speed not given, lets assume they are s1 and s2, in kmph
Lets assume the time to collision is t, then t=200/(s1+s2)
Again lets assume the bird meets one of the trains as it enters the tunnel. The distance the bird travels then will be equal to 1000/t=1000/200/(s1+s2)=5*(s1+s2)