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- Question
- 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
- Correct Answer
- 6 km/hr
ExplanationLet 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 - 1. 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
- 2. 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
- 3. 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 Discuss
- 4. 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
- 5. 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
- 6. 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
- 7. 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
- 8. A boat takes 3 hours to travel from place M to N downstream and back from N to M upstream. If the speed of the boat in still water is 4 km, what is the distance between the two places?
Options- A. 8 km
- B. 12 km
- C. 6 km
- D. Data inadequate Discuss
- 9. A motorboat can travel at 10 km/h in still water. It travelled 91 km downstream in a river and then returned to the same place, talking altogether 20 h. The rate of flow of river is?
Options- A. 3 km/h
- B. 4 km/h
- C. 2 km/h
- D. 5 km/h Discuss
- 10. A boat has to travel upstream 20 km distance from point X of a river to points Y. The total time taken by boat in travelling from point X to Y and Y to X is 41 min 40 s. What is the speed of the boat?
Options- A. 66 km/h
- B. 72 km/h
- C. 48 km/h
- D. Cannot be determined Discuss
Boats and Streams problems
Search Results
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: 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: 12 hrs
Explanation:
Speed 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.
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: 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.
Correct Answer: Data inadequate
Explanation:
Let the distance between M and N and the speed of current be d km and x km/hr respectively.
According to the question = {d/(4 + x) + d/(4 - x)} = 3
In the above equation we have only one equations but two variables. Hence cannot be determined (Data inadequate).
Correct Answer: 3 km/h
Explanation:
Given, speed of boat = 10 km/h
Let speed of flow of river = x km/h
? Upstream speed of boat = (10 - x) km/h
and downstream speed of boat = = (10 + x) km/h
According to question.
91/(10 - x) + 91/(10 + x) = 20
? 91(10 + x + 10 - x) / (10 - x) (10 + x) = 20
? 91(20) / 100 - x2 = 20
? 91 = 100 - x2
? x2 = 9
? x = 3
Correct Answer: Cannot be determined
Explanation:
Let x be the speed of the boat and y be the speed of the current.
Speed upstream = (x - y) km/h
Speed downstream = (x + y) km/h
According to the question,
20 /(x - y) + 20/(x + y) = 25/36
In this equation, there are two variables but only one equation. So, the value of x cannot be determined.
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