ibm - a policeman starts chasing a thief 30 minutes after the thief had run from a spot with an average speed of 20km per hour he takes 2 hours to catch the thief what is the average speed of the thief - skillgun

As given, the average speed of the policeman = 20km/hr.
He takes 2 hours to catch the thief, so from formula, "distance = speed x time" we have
The total distance covered by the police to catch the thief = 20 x 2 = 40 km (This value is also equal to the distance run by thief before being caught by Police.)
Policeman had started late by 30 minutes and took 2 hours to catch the running thief.
Above means that the thief takes (30minutes + 2 hours =) 5/2 hours to reach 40km.
So the speed of the thief = 40/(5/2) = 40 x 2 / 5 = 16 km/hr.
Hence the answer is 16km/hr.