Two goods train each 500 m long, are running in opposite directions on parallel tracks. Their speeds are 45 km/hr and 30 km/hr respectively Find the time taken by the slower train to pass the driver of the faster one.  Select the correct option.
A) 12 sec  B) 24 sec  C) 48 sec  D) 60 sec  E) none

Rationale: solution relative speed = ( 45 + 30 ) km / hr = ( 75 x 5 / 18 ) m / sec = ( 125 / 6 ) m / sec total distance covered = ( 500 + 500 ) m = 1000 m required time = ( 1000 x 6 / 125 ) sec = 48 sec answer c
Answer: C