Subject: General Aptitude · Chapter: Boats and Streams · Exam: · Marks: · Difficulty:
A boat can travel 36 km upstream in 5 hours. If the speed of the stream is 2.4 kmph, how much time will the boat take to cover a distance of 78 km downstream? (in hours) [United India Insurance Co. Ltd. (UIICL) Assistant (Online) Exam, 2015]
(a)5
(b)6.5
(c)5.5
(d)8
Answer
Answer (as printed): B
Explanation
Distance covered by a boat in 5 hours $=36$ km. Rate upstream of boat $=\frac{36}{5}=7.2$ kmph. Speed of stream $=2.4$ kmph. ∴ Speed of boat in still water $=(7.2+2.4)$ kmph $=9.6$ kmph. ∴ Rate downstream of boat $=(9.6+2.4)$ kmph $=12$ kmph. ∴ Time taken in covering 78 km distance $=\frac{78}{12}=6.5$ hours.
Explanation as extracted from the printed page; notation may be imperfect.