Question

A thief is spotted by a policeman from a distance of 200 metre. when the policeman starts the chase, the thief also starts running. assuming the speed of the thief to be 10 kmph, and that of the policeman to be 12 kmph, how far would the thief have run before he is overtaken?

Answer 1

will assume that the thief is running directly away from the policeman. (If he/she isn't, they are more likely to be caught).

 

You stated that the distance between them is 200m at first. The difference in their running speeds is 10 kph. In m/hr, this is 2000 m/hr. In order for the policeman to overtake the thief, he must shorten the distance to the thief to zero. This means he must run 100 m at a speed of 2000 m/h. Since 100 = 2000t yields t = 1/20 hr = 3 minutes, this is how long it will take the policeman to nab the crook.

 

In this same time, the thief will have run 8000 m/h times 1/20 hr = 400 meters.