A motorboat in still water travels at a speed of 36 km/hr. It goes 56 km upstream in 1 hour 45 monutes. The time taken by it to cover the same distance down the stream will be-
A. 1 hour 24 minutes
B. 2 hour 21 minutes
C. 2 hour 25 minutes
D. 3 hour
Answer: Option A
Solution(By Examveda Team)
$$\eqalign{ & {\text{Speed upstream}} \cr & {\text{ = }}\left( {\frac{{56}}{{1\frac{3}{4}}}} \right)km/hr \cr & = \left( {56 \times \frac{4}{7}} \right)km/hr \cr & = 32km/hr \cr & {\text{let speed downstream be }}x{\text{ km/hr}}{\text{.}} \cr & {\text{Then speed of boat in still water }} \cr & {\text{ = }}\frac{1}{2}\left( {x + 32} \right)km/hr \cr & \therefore {\text{ }}\frac{1}{2}\left( {x + 32} \right) = 36\,\,\, \Rightarrow x = 40 \cr & {\text{Hence , required time}} \cr & {\text{ = }}\left( {\frac{{50}}{{40}}} \right)hrs \cr & = 1\frac{2}{5}hrs \cr & = 1\,{\text{hour}}\,24\operatorname{minutes} \cr} $$Related Questions on Boats and Streams
A. 2 hours
B. 3 hours
C. 4 hours
D. 5 hours
E. None of these
A. 8.5 km/hr
B. 9 km/hr
C. 10 km/hr
D. 12.5 km/hr
E. None of these
A. 2 : 1
B. 3 : 2
C. 8 : 3
D. Cannot be determined
E. None of these
A. 4 km/hr
B. 5 km/hr
C. 6 km/hr
D. 10 km/hr
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