The speed of a boat in still water is 13 km/h, and the speed of the stream is 4 km/h. How much more time will it take to go upstream than ingoing downstream a distance of 68 km? (Correct to the nearest minute)
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 3 hours 33 minutes.
The speed of a boat in still water (x) = 13 km/h
The speed of the stream (y) = 4 km/h
Downstream speed = (x + y) = (13 + 4) = 17 km/h
Upstream speed = (x - y) = (13 - 4) = 9 km/h
Total distance (D) = 68 km
Time required to cover 68 km downstream = 68/17 = 4 hours
Time required to cover 68 km upstream = 68/9 = 7.555... hours ≈ 7.55 hours = 7 hours 33 minutes
The difference in time = 7 hours 33 minutes - 4 hours = 3 hours 33 minutes