A boat can travel with a speed of 12 km/hr in still water. If the speed of the stream is 4 km/hr, find the time taken by the boat to go 68 km downstream.  Choose the most appropriate option.
A) 4.25 hr  B) 5.25 hr  C) 8.25 hr  D) 2.25 hr  E) 2.50 hr

Rationale: "speed of boat in still water = 12 km / hr speed of the stream = 4 km / hr speed downstream = ( 12 + 4 ) = 16 km / hr time taken to travel 68 km downstream = 68 ⁄ 16 = 17 ⁄ 4 = 4.25 hours answer is a"
Answer: A