Boat And Stream

Q 1: A boat covers a certain distance downstream in 1 hour, while it comes back in 4 hours. If the speed of the stream be 6 kmph, what is the speed of the boat in still water? A)12 kmph B)10 kmph C)8 kmph. D)None of these Answer : Option B Explanation: Let the speed of the boat in still water be x kmph. Then, Speed downstream = (x + 6) kmph, Speed upstream = (x - 6) kmph. (x + 6)x 1=(x - 6)x 4 =>x + 6= 4x -24 =>x=30/3=10 kmph. Q 2: In one hour, a boat goes 14 km/hr along the stream and 6 km/hr against the stream. The speed of the boat in still water (in km/hr) is: A)8 kmph B)11 kmph C)7 kmph D)10 kmph Answer : Option D Explanation: Speed in still water=1/2(14+6) kmph = 10 kmph Q 3: Speed of a boat in standing water is 12 kmph and the speed of the stream is 2.5 kmph. A man rows to a place at a distance of 110 km and comes back to the starting point. The total time taken by him is: A)9 hour 16 minute B)15 hour 14 minute C)19 hour 16 minute D)10 hour 20 minute Answer : Option C Explanation: Speed upstream = 9.5 kmph. Speed downstream = 14.5 kmph. Total time taken=[(110/9.5)+(110/14.5)]hours=19 hour 16 minute. Q 4: A Boy's speed with the current is 20 km/hr and the speed of the current is 2.5 km/hr. The Boy's speed against the current is: A)15 km/hr B)25 km/hr C)14.5 km/hr D)18 km/hr Answer : Option A Explanation: Boy's rate in still water = (20 - 2.5) km/hr = 17.5 km/hr. Boy's rate against the current = (17.5 - 2.5) km/hr = 15 km/hr.

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