a motorboat whose speed is 9km/hr in still water,goes 15km downstream and comes back in a total time of 3hrs45min.find the speed of the stream?
Asked by aditya95 | 11th Aug, 2010, 07:54: PM
T = time for downstream, t = time for upstream travel.
T + t = 3 hrs 45 min = 15/4 hrs.
For downstream, distance/velocity = time,
15/(V + v) = T
15/(9 + v) = T ... (1)
15/(9 - v) = t ... (2) ...where V - Speed of boat, v - speed of stream.
Add (1) and (2)
15/(9 + v) + 15/(9 - v) = T + t
15(18)/(81 - v2) = 15/4
v2 = 81 - (18x4) = 9
v = sped of stream is 3 km/hr.
Answered by | 11th Aug, 2010, 09:51: PM
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