>> Aptitude >> Boat and Stream

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1). A boat goes 20 km upstream in 2 hours and downstream in 1 hour. How much time this boat will take to travel 30 km in all still water?
Let \( \Large v_{1} \) be the speed of boat in still water and \( \Large v_{2} \) be the speed of current | ||||

2). In the above question, the speed at which the stream is flowing is
Correct Answer: 5 km/hr
From the above two equation, we get \( \Large v_{2} \) = 5 km/hr | ||||

3). A boat travels 10 km in 1 hr downstream and 14 kms in 2 hrs upstream. How much time this boat will take to travel 17 kms in still water?
\( \Large v_{1} \) + \( \Large v_{2} \) = \( \Large \frac{10}{1} \) = 10 ...(i) \( \Large v_{1} \) - \( \Large v_{2} \) = \( \Large \frac{14}{2} \) = 7 ...(ii) Adding equations (i) and (ii), we get \( \Large v_{1} \) = \( \Large \frac{17}{2}km/hr \) \( \Large t = \frac{d}{v_{1}} = \frac{17}{\frac{17}{2}} \) = 2 hrs. | ||||

4). A man goes by motor boat a certain distance upstream at 15 km/hr and return the same downstream at 20 kin/hr. The total time taken for the journey was 7 hrs. Find how far did he go.
Correct Answer: 60 km
\( \Large \frac{d}{20}+\frac{d}{15}=7 \) Therefore, d = 60 km | ||||

5). A man can row upstream a distance of \( \Large \frac{2}{3} \) km in 10 minutes and returns the same distance downstream in 5 minutes. Ratio of man's speed in still water and that of the stream will be
\( \Large v_{1} \) - \( \Large v_{2} \) = \( \Large \frac{\frac{2}{3}km}{10 min} \) Therefore, \( \Large \frac{V_{1}}{V_{2}} = \frac{1}{10} \times \frac{30}{1} \) | ||||

6). A man can row a certain distance down stream in 6 hours and return the same distance in 9 hours. If stream flows at the rate of 2 km/hr, then what will be man's speed if he rows in still water?
\( \Large \left(v_{1}+v_{2}\right)t_{1} = \left(v_{1}-v_{2}\right)t_{2} \) | ||||

7). A boat against the current of water goes 9 km/hr and in the direction of the current 12 km/hr. The boat takes 4 hours and 12 minutes to move upwared and downward direction from A to B. What is the distance between A and B?
Correct Answer: 21.6 km
\( \Large \frac{d}{9}+\frac{d}{12}=4\frac{12}{60} \) | ||||

8). A man takes 3 hours and 45 minutes to boat 15 km with the current in a river and 2 hours 30 minutes to cover a distance of 5 km against the current. Speed of the boat in still water and speed of the current respectively will be
\( \Large V_{1} + V_{2} = \frac{15}{3\frac{3}{4}} \) = 4 km/hr ... (1) | ||||

9). A boat can be rowed 6 km/hr along the current and 4 km/hr against the current. Speed of the current and speed of the boat in still water, respectively will be
\( \Large v_{1} \) + \( \Large v_{2} \) = 6 ....(i) \( \Large v_{1} \) - \( \Large v_{2} \) = 4 ...(ii) From equations (i) and (ii), we get \( \Large v_{1} = 5 km/hr \) and = \( \Large v_{2} = 1 km/hr \) | ||||

10). A boat moves down the stream at the rate of 1 km in 6 minutes and up the stream at the rate of 1 km in 10 minutes. The speed of the current is
\( \Large v_{1} \) + \( \Large v_{2} \) = \( \Large \frac{1km}{6km}= 10 km/hr \) ....(i) |