Boats and Streams: Practice Questions

1. A man takes 20 minutes to row 12 km upstream which is a third more than the time he takes on his way downstream. What is his speed in still water?
A. 41 km/hr
B. 36 km/hr
C. 42 km/hr
D. 45 km/hr
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2. How long will it take to row 20 km upstream if one can row 10 km in 10 minutes in still water and the same distance in 8 minutes with the stream?
A. 12 min
B. 13.33 min
C. 24 min
D. 26.67 min
Q.3. A boat makes a return journey from point A to point B and back in 5 hours 36 minutes. One way it travels with the stream and on the return it travels against the stream. If the speed of the stream increases by 2 km/hr, the return journey takes 9 hours 20 minutes. What is the speed of the boat in still water? (The distance between A and B is 16 km.)
A. 5 km/hr
B. 3 km/hr
C. 7 km/hr
D. 9 km/hr
Q.4. A boat travels from point A to B, a distance of 12 km. From A it travels 4 km downstream in 15 minutes and the remaining 8 km upstream to reach B. If the downstream speed is twice as high as the upstream speed, what is the average speed of the boat for the journey from A to B?
A. 10(2/3)km/hr
B. 9.6 km/hr
C. 11.16 km/hr
D. 10.44 km/hr
Q.5. A man rows ‘k’ km upstream and back again downstream to the same point in H hours. The speed of rowing in still water is s km/hr and the rate of stream is r km/hr. Then
A. (s2-r2) =2sk /H
B. (r + s) = kH / (r -s)
C. rs = kH
D. None of the above
Q.6. A man rows 24 km upstream in 6 hours and a distance of 35 km downstream in 7 hours. Then the speed of the man in still water is
A. 4.5 km/hr
B. 4 km/hr
C. 5 km/hr
D. 5.5 km/hr
Q.7. A boat goes 12 km upstream in 48 minutes. The speed of stream is 2 km/hr. The speed of boat in still water is
A. 15 km/hr
B. 16 km/hr
C. 17 km/hr
D. 18 km/hr
Q8. A motorboat can travel at 5 km/hr in still water. It travelled 90 km downstream in a river and then returned, taking altogether 100 hours. Find the rate of flow of the river.
A. 3 km/hr
B. 3.5 km/hr
C. 2 km/hr
D. 4 km/hr
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Q9. A boatman can row 2 km against the stream in 20 minutes and return in 10 minutes. Find the rate of flow of the current.
A. 2 km/h
B. 1 km/h
C. 3 km/h
D. 5 km/h
Q10. A man can row 30 km upstream in 6 hours. If the speed of the man in still water is 6 km/hr, find how much he can row downstream in 10 hours.
A. 70 km
B. 140 km
C. 200 km
D. 250 km
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