A boy rows 1500m in 1350 seconds against the stream and returns in 15 minutes. His rowing speed in still water is. A) 5km/hr B) 4km/hr C) 7km/hr D) 9km/hr

1 Answer

Answer :

ANSWER : A

 Explanation:

 Rate upstream = (1500 / 1350) m/s = (150/135) m/s

= 10/9 m/s

 Rate downstream = (1500 / 900)m/s = (15/9)m/s

 = 5/3 m/s

 Rate in still water = ½ [ a+ b]

 = ½[10 / 9 + 5 /3]

 = ½[10 +15 / 9]

 = ½[25/9]

 = 25/18 m/s

 = (25/18) * (18/5)km/hr

 speed in still water = 5km/hr

Related questions

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Description : A mototboat can row to a place 112 km away and come back in 44 hours. The time to row 42 km with the stream is same as the time to row 24 km against the stream. Find the speed of boat in still water. A) 5.5 km/hr B) 7.5km/hr C) 10.5 km/hr D) 3.5 km/hr 

Last Answer : ANSWER: A Explanation: Downstream speed = 42/x km/hr Upstream speed = 24/x km/hr 112 / (42 / x) + 112 / (24 / x) = 44 112[x /42 + x / 24] = 44 112 / 3 [x / 14 + x / 8] = 44 11x / 56 = 44 * ... = 4 km/hr Speed of boat = 1/2 * (7 + 4) km/hr = 11 /2 speed of boat in still water = 5.5 km/hr

Description : A boatman can take the same time to row6.5km downstream and 3.5km upstream. His speed in still water 2.5 km/hr. The speed of the stream is. A) 0.75 km/hr B) 2.5 km/hr C) 1.5km/hr D) 7.5km/hr

Last Answer : ANSWER: A Explanation: Given that the speed in still water = 2.5 km/hr Let the speed of the stream be x; km/hr speed in upstream = (2.5 - x)km/hr Then time taken to cover 6.5 km downstream = 6.5 / (2.5+x) ... 5x = 8.75 + 3.5x 10 x = 7.5 x = 0.75 km/hr The speed of the stream is 0.75 km/hr

Description : A boat takes 27 hrs to travel a distance upstream and takes 9hrs to travel the same distance downstream. If the speed of the boat in still water is 12km/hr, then what is the velocity of the stream? A) 8km/hr B) 6km/hr C) 4km/hr D) None of these

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Description : A motorboat can cover 80 km upstream and 120 km downstream together in 26 hours. Also it can cover 100 km upstream and 144 km downstream together in 32 hours. What is the speed of the motorboat in still water? A) 12 km/hr B) 15km/hr C) 8.5km/hr D) 19km/hr 

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Description : A boat man lakes 5hrs 30 mins to row a boat 30km downstream of a river and 4 hrs 15mints to cover a distance of 10km upstream. Find the speed of the river current in km/hr. A) 1.5 km/hr B) 3km/hr C) 5km/hr D) 7 km/hr

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Description : A girl can row 15 kmph in still water and he finds that it takes him thrice as long to row up as to row down the river. Find the rate of stream. A) 2.5 B) 5.5 C) 7.5 D) 12.5 

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Description : There are 3 poles M, N and O in a straight line such that point N is equidistant from points M and O. A boat can travel from point M to O downstream in 6 hours and from N to M upstream in 4 hours. Find the ratio of boat in still water to speed of stream. A) 2:3 B) 7:1 C) 3:2 D) 1:7

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Description : Dhanvanth can swim at 15 km/hr in stagnant water. In a river with 3 km/hr current, he swims to a certain distance and comes back within 100 min. What is the distance between the two points? A) 11km B) 13km C) 19km D) 12km

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Description : There is a bridge besides a river. Two friends Arun and varun started their journey from place L, moved to the garden located at another place M & then returned to place L. Arun moves by swimming at a speed of 30 ... 12km/hr, what will be the average speed of boat sailor? A) 36 B) 18 C) 24 D) 48 

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Description : A man rows to a place 48km distant and back in 14 hours. He finds that he can row 4km with the stream in the same time as 3km against the stream. Find the rate of the stream. A.2 km/hr B.1 km/hr C.3 km/hr D.3.5km/hr

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Description : Mohana can row 80km upstream and 110km downstream in 26 hrs. Also she can 60km upstream and 88km downstream in 20 hrs. Find the speed of the girl in still water and the speed of the current in ratio: A) 5:6 B) 3:6 C) 7:9 D) 8:3 

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Description : A motor boat sails 30 km of a river towards upstream in 10hrs. How long will it take to cover the same distance downstream, if the speed of the current is ½ of the speed of the boat in still water. A) 1.8hrs B) 3.33hrs C) 5hrs D) None of these

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Description : A boat takes 24 hours to cover 128 km downstream and 16 hours to cover 64 km upstream. Then the speed of the boat in still water is: A) 14/3 B) 8/7 C) 3/2 D) 9/5

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Description : A motorboat running upstream takes 4 hrs 24 mins to cover a certain distance, while it takes 2hrs to cover the same distance running downstream. What is the ratio between the speed of the boat and speed of the water current respectively? A) 8:3 B) 5:2 C) 3:7 D) 2:4

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Last Answer : ANSWER : B 

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Description : A bike starts with a speed of 60 km/hr at 8a.m. Due to the problem in engine it reduces its speed as 20 km/hr for every 1 hour. After 9 am, the time taken to covers 15 km is: a) 13 minutes and 20 seconds b) 15 minutes and 09 seconds c) 18 minutes and 15 seconds d) 22 minutes and 30 seconds

Last Answer : 15 min

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Description : Distance between two stations P & Q is 1556km. A passenger train covers the journey from P to Q at 168km per hr and return back to P with a uniform speed of 112km/hr. Find the Average speed of the train during the whole journey? A) 124.4 km/hr B) 130.4km/hr C) 134.4 km/hr D) 130.0 km/hr

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