A) 1 : 2
B) 1 : 3
C) 1 : 4
D) 2 : 3
Correct Answer: C
Solution :
[c] Let speed of boat in still water = x km/hr Let speed of stream = y km/hr Let distance covered = d km \[\therefore \] \[\frac{d}{x+y}=\frac{45}{60}=\frac{3}{4}\] ? (1) \[\frac{d}{x-y}=\frac{75}{60}=\frac{5}{4}\] ? (2) From (1) & (2), \[\frac{x-y}{x+y}=\frac{3}{5}\Rightarrow 5x-5y=3x+3y\] \[\Rightarrow 2x=8y\Rightarrow \frac{y}{x}=\frac{1}{4}\] \[\therefore \] Ratio of speed of the stream to boat in still water = 1 : 4You need to login to perform this action.
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