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A boat goes 2 km against the current in 1 hour and 1 km along the current in 10 minutes. How long will it take to travel 5 km in still water?
A1 hour 15 minutes
B40 minutes
C1 hour
D1 hour 30 minutes
Answer & Solution
Correct answer: A. 1 hour 15 minutes
1. Upstream speed = 2 km/h; downstream speed = 1 km in 10 min = 6 km/h.
2. Speed in still water = (downstream + upstream)/2 = (6 + 2)/2 = 4 km/h.
3. Time for 5 km = 5/4 h = 1.25 h = 1 hour 15 minutes.
_Source: RRB Group D (RRC) PYQ, held 27-10-2013, Q.48._