A man can row at a speed of $$4\frac{1}{2}$$ km/hr in still water. If he takes 2 times as long to row a distance upstream as to row the same distance downstream, then the speed of stream (in km/hr) is-
A. 1
B. 1.5
C. 2
D. 2.5
Answer: Option B
Solution(By Examveda Team)
$$\eqalign{ & {\text{Speed of man in still water , }} \cr & x{\text{ }} = {\text{ }}\frac{9}{2}km/hr{\text{ }} \cr & {\text{let speed of stream = }}y{\text{ }}km/h \cr & {\text{Downstream speed = }} {\frac{9}{2} + y} \cr & {\text{Upstream speed = }} {\frac{9}{2} - y} \cr & {\text{Accroding to questions,}} \cr & {\text{2}} \times {\frac{{{\text{Distance}}}}{{ {\frac{9}{2} + y} }}} = \frac{{{\text{Distance}}}}{{ {\frac{9}{2} - y} }} \cr & \Rightarrow \frac{2}{{\frac{9}{2} + y}} = \frac{1}{{\frac{9}{2} - y}} \cr & \Rightarrow \frac{{2 \times 2}}{{9 + 2y}} = \frac{2}{{9 - 2y}} \cr & \Rightarrow \frac{2}{{9 + 2y}} = \frac{1}{{9 - 2y}} \cr & \Rightarrow 18 - 4y = 9 + 2y \cr & \Rightarrow 6y = 9 \cr & \Rightarrow y = \frac{9}{6} = \frac{3}{2} = 1.5\,km/h \cr} $$Join The Discussion
Comments ( 1 )
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
thanks