Aptitude Boats and Streams Test Paper 26) A man swimming in a river which is flowing at 3 km/hr finds that in a given time he can swim twice as far downstream as he can swim upstream. What will be his speed in still water?
The correct answer is C Answer with explanation: Let the man swims at X km/hr in still water. As per the question, he covers twice the distance downstream as he covers upstream in a given time. Distance = Speed ∗ Time ∴ Speed downstream ∗ Time = 2 (Speed upstream ∗ Time) Time is same in both the cases. ∴ X+3 =2∗ X  3 X + = 2∗ X  X + =2X  7 X2X = 7  X = = 10.5 km/hr 7) A man can row at 12 km/hr in still water. He finds that he takes twice as much time to row upstream than to row downstream when he covers a certain distance. Find the speed of the stream.
The correct answer is A Answer with the explanation: As per the question, he takes twice the time when he rows upstream than rowing downstream. Time is inversely proportioned to speed. So he rows at twice the speed when moving along the stream than moving against the stream. Let his speed upstream = X km/hr And, his speed downstream = 2X ∴ Speed in still water = 1/2 (2X+X) = 1.5 X km/hr As per the question; 1.5X = 12 km/hr X = =8 km/hr Speed upstream = 8 km/hr So, speed downstream = 2 ∗ 8= 16 km/hr Speed of current = (speed downstream  speed upstream) = (16  8) = * 8 = 4 km/hr 8) A boat takes 6 hours to move downstream from point P to Q and to return to point P moving upstream. If the speed of the stream is 4 km/hr and speed of the boat in still water is 6 km/hr, what is the distance between point P and Q?
The correct answer is C Answer with the explanation: Let the distance between points P and Q = X km Speed downstream = 6 + 4= 10 km/hr Speed upstream = 6  4 = 2 km/hr Time = So, as per question; + = 6 hours = 6 6X = 60 X = 10 km 9) A man can swim in still water at 8 km/hr. If the river is flowing at 2km/hr he takes 80 minutes to reach a place and return back, how far is the place?
The correct answer is D Answer with the explanation: Let the place is X km far. Speed downstream = 8+2=10 km/hr Speed upstream = 8  2 = 6 km/hr Time = So, as per question; + = = 30X + 18X = 240 48X = 240 X = = 5 km 10) A motorboat travels 16 km in 2 hours against the flow of river and travels next 8 km along the flow of the river in 20 minutes. How long will it take motorboat to travel 48 km in still water?
The correct answer is B Answer with the explanation: Speed = Speed upstream = = 8 km/hr Speed downstream = = = 24 km/hr ∴ Speed in still water = (speed downstream +speed upstream) = (24+8)=16 km/hr Required time = = =3 hour Aptitude Boats and Streams 1 Aptitude Boats and Streams 3 Aptitude Boats and Streams 4 Boats and Streams Concepts
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