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- Question
- The speed of the current is 5 km/h. A motorboat goes 10 km upstream and back again to the starting point in 50 min. The speed, (in km/h) of the motorboat in still water is?
Options- A. 20 km/h
- B. 26 km/h
- C. 25 km/h
- D. 28 km/h
- Correct Answer
- 25 km/h
ExplanationLet speed of boat be x km/h.
Given speed of current = 5 km/h
? Upstream speed of boat = (x -5) km/h
Downstream speed of boat = (x + 5) km/h
According to the question.
10/(x - 5) + 10/(x + 5) = 50/60
? 10(x + 5 + x - 5)/( x2 - 25) = 5/6
? x2 -24x - 25 = 0
? x2 - 25x + x - 25 = 0
? (x - 25) (x + 1) = 0
? x = 25 [? x ? -1] - 1. A man can row 6 km/h in still water. If the speed of the current is 2 km/h, it takes 3 h more in upstream than in the downstream for the same distance. The distance is?
Options- A. 30 km
- B. 24 km
- C. 20 km
- D. 32 km Discuss
- 2. Pawan can row 24 km/h in still water. When the river is running at 4.8 km/h, it takes him 1 h to row to a place and to come back. How far is the place?
Options- A. 11.52 km
- B. 14 km
- C. 12.52 km
- D. 15 km Discuss
- 3. Sameer can row a certain distance downstream in 24 h and can come back covering the same distance in 36 h. If the stream flows at the rate of 12 km/h, find the speed of Sameer in still water?
Options- A. 30 km/h
- B. 15 km/h
- C. 40 km/h
- D. 60 km/h Discuss
- 4. A sailor sails a distance of 48 km along the flow of a river in 8 h. If it takes 12 h to return the same distance, then the speed of the flow of the river is?
Options- A. 0.5 km/h
- B. 1 km/h
- C. 1.5 km/h
- D. 2 km/h Discuss
- 5. speed of a boat in standing water is 7 km/hr and the speed of the stream is 1.5 km/hr. A distance of 7.7 km. going upstream is covered in?
Options- A. 1 hr. 15 min.
- B. 1 hr. 12 min.
- C. 1 hr. 24 min.
- D. 2 hr. 6 min. Discuss
- 6. A boat cover a distance of 30 km downstream in 2 h while it takes 6 h to cover the same distance distance upstream. What is the speed of the boat (in km/h)?
Options- A. 5
- B. 7.5
- C. 13
- D. 10 Discuss
- 7. A man can row at 10 km/h in still water. If he takes total 5 h to go to a place 24 km away and return, then the speed of the water current is?
Options- A. 2 km/h
- B. 3 km/h
- C. 1/2 km/h
- D. 1 km/h Discuss
- 8. Ashutosh can row 24 km/h in still water. It takes him twice as long to row up as to row down the river. Find the rate of stream.?
Options- A. 4 km/h
- B. 18 km/h
- C. 8 km/h
- D. 15 km/h Discuss
- 9. A boat goes 12 km in 1 h in still water. It takes thrice time in covering the same distance against the current. Find the speed of the current.?
Options- A. 8 km/h
- B. 12 km/h
- C. 6 km/h
- D. 7 km/h Discuss
- 10. A boatman takes twice as long to row a distance against the stream as to row the same distance with the stream. Find the ratio of speeds of the boat in still water and the stream.?
Options- A. 2 : 1
- B. 3 : 1
- C. 1 : 2
- D. 1 : 3 Discuss
Boats and Streams problems
Search Results
Correct Answer: 24 km
Explanation:
Let total distance be x km.
According to the question,
x/(6 + 2) + 3 = x/6 - 2
? x/8 + 3 = x/4
? x/4 - x/8 = 3
? 2x - x/8 = 3
? x = 8 x 3 = 24 km
Correct Answer: 11.52 km
Explanation:
Pawan's speed downstream = 24 + 4.8 = 28.8 km/h
Pawan's speed upstream = 24 - 4.8 = 19.2 km/h
Let the required distance be x.
According to the question.
x/28.8 + x/19.2 = 1
? (19.2x + 28.8x) / 552.96 = 1
? 19.2x + 28.8x = 552.96
? 48x = 552.96
? x = 552.96/48 = 11.52 km
Correct Answer: 60 km/h
Explanation:
Let the speed of Sameer in still water be x km/h
Sameer's speed downstream = (x + 12) km/h
Sameer's speed upstream = (x - 12) km/h
According to the question, 24(x + 12) = 36(x - 12)
? 2x + 24 = 3x - 36
? x = 36 + 24 = 60 km/h
Correct Answer: 1 km/h
Explanation:
Let speed of the flow of water be x km/h and rate of sailing of sailor be y km/h.
Downstream speed (x + y) = 48/8
? x + y = 6 ....(i)
and upstream speed x - y = 4 ...(ii)
On solving Eqs. (i) and (ii), we get
y = 1 km/h
Correct Answer: 1 hr. 24 min.
Explanation:
Upstream speed = 7 - 1.5 = 5.5 km/hr
? 5.5 x T = 7.7
? T = 77.7 / 5.5 = 1hr. 24 minutes
Correct Answer: 10
Explanation:
Speed of boat downstream = Distance covered / Time taken
= 30/2 = 15 km/h
Now, speed of boat upstream = Distance covered / Time taken
= 30/6 = 5 km/h
Now, speed of boat = (Speed download + Speed upstream) / 2
= (15 + 5) / 2 = 10 km/h
Correct Answer: 2 km/h
Explanation:
Let speed of water current be x km/h
? Speed downstream = (10 + x) km/h.
Speed upstream = (10 - x) km/h
According to the question,
24/(10 + x) + 24/(10 - x) = 5
? 24[10 - x + 10 + x] = 5(102 - x2)
? 100 - x2 = (24 x 20) / 5
? 100 - x2 = 96
? x2 = 4
? x = ?4 = 2km/h
Correct Answer: 8 km/h
Explanation:
Let rate of stream be 'a' km/h.
According to the question.
24 + a = 2(24 - a)
? 24 + a = 48 - 2a
? 3a = 48 - 24 = 24
? a = 24/3 = 8 km/h
Correct Answer: 8 km/h
Explanation:
Speed of a boat in still water = distance / time = 12/1 = 12 km/h
Speed against the current = 12/3 km/h
Let the speed of the current = x km/h
According to the question,
12 - x = 4
? x = 8 km/h
Correct Answer: 3 : 1
Explanation:
Let boatman's speed upstream x
And his speed downstream = 2x
? Ratio = (Speed in still water) : (Speed of stream)
= (2x + x/2) : (2x - x/2)
= 3x/2 : x/2
= 3 : 1
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