How fast is this dog?
A thief escapes from a prison. When he was at a distance of 5km from the prison, the police start chasing him with a speed of 20m/s. The thief is running away with speed 10m/s. A police dog starts running as soon as the police starts, with a speed of 30m/s and runs back and forth from the police to the thief and back to the police till the police catch the thief.
In kilometers, find the distance that the dog ran in the forward direction only.