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- Question
- 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
- Correct Answer
- 2 km/hr
ExplanationLet 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
- 1. 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
- 2. 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
- 3. 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
- 4. The ratio of speed of a motorboat to that of the current of water is 35 : 5. The motorboat goes along with the current in 5 h 10 min. Find the time to come back of motorboat?
Options- A. 5 h 50 min
- B. 6 h
- C. 6 h 50 min
- D. 12 h 10 min Discuss
- 5. A man can row 7 1/ 2 km/h in still water. If in a river running at 1.5 km/h, it takes him 50 min to row to a place and back, how far off is the place?
Options- A. 3 km
- B. 4 km
- C. 1 km
- D. 2 km Discuss
- 6. 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
- 7. 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
- 8. 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
- 9. 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
- 10. 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
Boats and Streams problems
Search Results
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: 6 h 50 min
Explanation:
Let speed of a motorboat be = 36k km/h
and speed of the current = 5k km/h
? Speed downstream = (36 + 5)k = 41k km/h
and speed upstream = (36 - 5)k = 31k km/h
Let distance be D km.
According to the question
When boat goes along with the current.
Distance = Time x Speed
? D = (5 + 10/60) x 41k
? D = 31/6 x 41k ....(i)
Again, when boat come back
a = Time x Speed
From Eq. (i) .
31/6 x 41k = Time x 31k
? Time = 41/6
Time = 6 h 50 min.
Correct Answer: 3 km
Explanation:
Let the distance be L km.
Speed of the main in still water = 71/2 km/h
and speed of the river = 15 km/h
? Speed of the man downstream = 7.5 + 1.5 = 9
Speed of the man upstream = 7.5 - 1.5 = 6 km/h
According to the question,
L/9 + L/6 = 50/60
? (4L + 6L)/36 = 50/60
? 10L/36 = 50/60
? L = (50 x 36)/(10 x 60)
5? x = 3 km
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: 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: 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
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