Karan and Arjun were assigned to visit two different sites for inspection. The distances of these sites from their office are 36 km and 48 km respectively. Both leave the office at the same time and reach their sites at 11
A.M. One day, their sites are interchanged, and Karan started 18 minutes earlier than Arjun to reach his assigned site on time. Find the speed of Karan.

Distance covered by Karan and Arjun = 36 km and 48 km, respectively.
Since, both of them reached their respective places at same time.
Therefore, ratio of speeds of Karan and Arjun = 36:48 = 3:4.
Let the speeds of Karan and Arjun be 3x km/hr and 4x km/hr, respectively.
Time taken by Karan to reach his place on the day of interchange = 48/3x hours.
Time taken by Arjun to reach his place on the day of interchange = 36/4x hours.
ATQ, (48/3x) – (36/4x) = 18/60.
Or, 16/x - 9/x = 0.3.
Or, 7/x = 0.3.
Or, 3x = 70.
So, speed of Karan = 3x = 70 km/hr.
Hence, the correct answer is A.