Aptitude Hack#17(12-3-19)

Question:

A boat covers a certain distance downstream in 1 hour, while it comes back in 1.5 hours. If the speed of the stream be 3 Kmph, what is the speed of the boat in still water?

A. 12 kmph
B. 13 kmph
C. 14 kmph
D. 15 kmph
 E.None of these
 Answer: D) 15 kmph


Explanation:

Let the speed of the boat in still water be x kmph. Then,

Speed downstream = (x + 3) kmph,

Speed upstream = (x - 3) kmph.

 (x + 3) x 1 = (x - 3) x 3/2

 2x + 6 = 3x - 9

 x = 15 kmph.