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# Ratio of speeds

PQ is a railway tunnel of length L km A dog sit sat a distance of 5L/11from P . If he hears a train coming towards point P then he runs toward it such that he collides with the train at point P . Instead if he runs towards Q then the accident happens at Q . Now find the Ratio of the speed of the train to that of the dog ( My answer is 11:1 but i am not quite sure about it ) Also what is the fastest way to solve such kinds of problems ?

Note by Avn Bha
2 years, 8 months ago

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Meeting at p: train travelled x km. dog travelled 5l/11. Therefore, x/(v+u)=(5l/11)/(v+u) wherr v=speed of train, u=speed of dog. Meetimg at q: train travelled x +l and dog travelled 6l/11. (X+l)/(v-u)=(6l/11)/(v-u)

Solve for the unknowns. The idea here is that the time it took for them to meet on both occasions is the same.

- 2 years, 8 months ago

how can x/(v+u)=(5L/11)/(v+u). if so then we get x=5L/11?. also if they have same time and same distance then wouldn't their speeds be the same ?

- 2 years, 8 months ago

Speed of train / speed of dog=11/3

- 2 years, 8 months ago