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- Question
- A man can swim 3 km/hr in still water. If the velocity of the stream be 2 km/hr, the time taken by him to swim to a place 10 km upstream and back is?
Options- A. 81/3 hrs
- B. 91/5 hrs
- C. 10 hrs
- D. 12 hrs
- Correct Answer
- 12 hrs
ExplanationSpeed upstream = (3 - 2) km/hr = 1 km/hr
Speed downstream = (3 + 2) km/hr = 5 km/hr
Total time taken = (10/1 + 10/5) hr = 12 hrs. - 1. A boat travels upstream from B to A and downstream from A to B in 3 hours. If the speed of the boat in still water is 9km/hr and the speed of the current is 3 km/hr the distance between A and B is?
Options- A. 4 km
- B. 6 km
- C. 8 km
- D. 12 km Discuss
- 2. A boat covers 24 km upstream and 36 km downstream in 6 hours while it covers 36 km upstream and 24 km downstream in 6 1/ 2 hours. The velocity of the current is?
Options- A. 1.5 km/hr
- B. 1 km/hr
- C. 2 km/hr
- D. 2.5 km/hr Discuss
- 3. A man 8 km/hr in still water. If the river is running at 2 km/hr, it taken 32 minutes to row to a place and back. How for is the place?
Options- A. 1.5 km
- B. 2.5 km
- C. 2 km
- D. 3 km Discuss
- 4. A boatman row 1 km in 5 min along the steam and 6 km in 1 h against the stream. The speed of the steam is?
Options- A. 3 km/h
- B. 6 km/h
- C. 10 km/h
- D. 12 km/h Discuss
- 5. Ravi can row downstream at 9 km/h and upsteam at 5 km/h. Find the speed of Ravi in still water and speed of current.
Options- A. 7 km/h and 2 km/h
- B. 8 km/h and 6 km/h
- C. 7 km/h and 3 km/h
- D. 8 km/h and 2 km/h Discuss
- 6. A man can row three quarters of a kilometre against the stream in 11 1/ 4 minutes and return in 7 1/ 2 minutes. The speed of the man in still water is?
Options- A. 2 km/hr
- B. 3 km/hr
- C. 4 km/hr
- D. 5 km/hr Discuss
- 7. A man can row 9 1/ 3 in still water and he finds that it takes him thrice as much time to row up than as to row down the same distance in river. The speed of the current is?
Options- A. 31 / 3 km/hr
- B. 31/3 km/hr
- C. 11/4 km/hr
- D. 42/3 km/hr Discuss
- 8. The current of a stream runs at 1 km/hr. A motor boat goes 35 km upstream and back again to the starting point in 12 hours. The speed of motor boat in still water is?
Options- A. 6 km/hr
- B. 7 km/hr
- C. 8.5 km.hr
- D. 8 km/hr Discuss
- 9. A man rows to a place 48 km distant and back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is?
Options- A. 0.5 km/hr
- B. 1 km/hr
- C. 3.5 km/hr
- D. 1.8 km/hr Discuss
- 10. Speed of a boat in standing water is 6 km/hr and the speed of the stream is 1.5 km/hr. A man rows to a place at a distance of 22.5 km and comes back to the starting point. The total time taken by him, is?
Options- A. 6 hrs 30 min
- B. 8 hrs 24 min
- C. 8 hrs
- D. 4 hrs 12 min Discuss
Boats and Streams problems
Search Results
Correct Answer: 12 km
Explanation:
Speed downstream = (9 + 3) km/hr = 12km/hr
Speed upstream = = (9 - 3) km/hr = 6km/hr
Let the distance AB = d km
Then, d/6 + d/12 = 3
? 2d + d = 36
? d = 12
? Distance AB = 12 km
Correct Answer: 2 km/hr
Explanation:
Let the speed upstream be U km/hr and the speed downstream be V km/hr respectively.
Then 24/U + 36/V = 6 ...(i)
and 36/U + 24/V = 13/2 ...(ii)
Solving these 2 equations we get
? U = 8 km/hr and V = 12 km/hr
? Velocity of current = (12 - 8)/2 km/hr = 2 km/hr
Correct Answer: 2 km
Explanation:
? D/(8 - 2) + D/(8 + 2) = 32/60
? D/6 + D/10 = 32/60
? 10D + 6D = 32
? D = 2 km
Correct Answer: 3 km/h
Explanation:
Let the speed of boat and steam be x and y km/h.
? Speed of boat along steam = (x + y) km/h
and speed of boat against stream = (x - y) km/h
According to the question,
x + y = 1 / (5/60) = 60/5
? x + y = 12 ...(i)
and y - x = 6 ...(ii)
On adding Eqs. (i) and (ii), we get
2x = 18
x = 18/2 = 9
On putting the value of x in Eq. (i), We get
9 + y = 12
y = 12 - 9 = 3
Hence, speed of boat = 9 km/h
and speed of steam = 3 km/h
Correct Answer: 7 km/h and 2 km/h
Explanation:
Given, downstream speed = 9 km/h
and upstream speed = 5 km/h
According to the formula
Ravi's speed in still water = (Speed downstream + Speed upstream )/2
= 1/2(9 + 5) = 14/2 = 7 km/h
and speed of current = (Speed downstream - Speed upstream)/2
= (9 - 5)/2 = 4/2 = 2 km/h.
Correct Answer: 5 km/hr
Explanation:
Speed upstream = (3/4) x (4/45 x 60 km/hr = 4 km/hr
Speed upstream = (3/4) x (2/15) x 60 km/hr = 6 km/hr
? Speed in still water = (4 + 6)/2 km/hr = 5 km/hr
Correct Answer: 42/3 km/hr
Explanation:
Let speed upstream = x km/hr
Then, speed downstream = 3x km/hr
? Speed in still water = (x + 3x)/2 km/hr = 2x km/hr
Speed of the current = (3x - x)/2 km/hr = x km/hr
&becaus 2x = 28/3
? x = 14/3 = 42/3 km/hr.
Correct Answer: 6 km/hr
Explanation:
Let the speed in still water be x km/hr
? 35/(x - 1) + 35/(x + 1) = 12
? 35(2x) = 12(x2 - 1)
? 12x2 - 70x - 12 = 0
? 12x2 - 72x + 2x - 12 = 0
? 12x(x - 6) + 2 (x - 6) = 0
? (x - 6) (12x + 2) = 0
? x = 6 km/hr
Correct Answer: 1 km/hr
Explanation:
Suppose he moves 4 km downstream in H hrs.
Then, Speed downstream = 4/H km/hr
Speed upstream = 3/H km/hr
T1 + T2 = 14
? (48 x H)/4 + (48 x H)/3 = 14
? 12H + 16H = 14
? H = 1/2
? Speed downstream = 8 km/hr
Speed upstream = 6 km/hr
? Rate stream = (8 - 6)/2 km/hr = 1 km/hr
Correct Answer: 8 hrs
Explanation:
Speed upstream = (6 - 1.5) km/hr = 4.5 km/hr
Speed downstream = (6 + 1.5) km/hr = 7.5 km/hr
Total time taken = (22.5/4.5 + 22.5/7.5) hrs
= (5 + 3) hrs.
= 8 hrs.
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