A boat can travel at a speed of 42 km/hr in still water. If the speed of the stream is 3 km/hr, how much time (in hours and minutes) will be taken by the boat to go 157.5 km downstream, and then 78 km upstream?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e 5 h 30 min.
Downstream speed = 42 + 3 = 45 km/h
Upstream speed = 42 - 3 = 39 km/h
Time for downstream = Distance ÷ Speed = 157.5 ÷ 45 = 3.5 hours
Time for upstream = 78 ÷ 39 = 2 hours
Total time = 3.5 hours + 2 hours = 5.5 hours = 5 hours 30 minutes