Boats and Streams problems
- 1. A person can row 8 1/2 km an hour in still water and he finds that it takes him twice as long to row up as to row down the river. The speed of the stream ?
Options- A. 1.78 kmph
- B. 2.35 kmph
- C. 2.83 kmph
- D. 3.15 kmph Also asked in: AIEEE, Bank Exams, CAT, GATE, Bank Clerk, Bank PO
Correct Answer: 2.83 kmph
Explanation:
Given speed of the person = 8 1/2 = 17/2 kmph
Let the speed of the stream = x kmph
speed of upstream = 17/2 - x
speed of downstream = 17/2 + x
But given that,
2(17/2 - x) = 17/2 + x
=> 3x = 17/2
=> x = 2.83 kmph.
- 2. Amith can row a boat d km upstream and the same distance downstream in 5 hours 15 minutes. Also, he can row the boat 2d km upstream in 7 hours. How long will it take to row the same distance 2d km downstream for Amith ?
Options- A. 4 hrs 10 min
- B. 3 hrs 15 min
- C. 3 hrs 30 min
- D. 4 hrs 1 min Also asked in: GATE, Bank Clerk, Bank PO, AIEEE, Bank Exams, CAT
Correct Answer: 3 hrs 30 min
Explanation:
Let the speed of boat and stream be x and y kmph respectively.
According to question
d/x+y + d/x-y = 5h 15m or 21/4 hrs ......(i)
and 2d/x-y = 7...... (ii)
From eq. (i) and (ii)
2d/x+y = 7/2
Hence, Amith will take to row 2d km distance downstream in 7/2 hrs
= 3.5 hrs
= 3 hrs 30 min.
- 3. A motorboat running upstream takes 8 hours 48 minutes to cover a certain distance, while it takes 4 hours to cover the same distance running downstream. What is the ratio between the speed of the motorboat and speed of the water current respectively?
Options- A. 3:7
- B. 7:9
- C. 5:4
- D. 8:3 Also asked in: AIEEE, Bank Exams, CAT, GATE, Bank Clerk, Bank PO
Correct Answer: 8:3
- 4. Sravan drove from home to a neighboring town at the speed of 50 km/h and on his returning journey, he drove at the speed of 45 km/h and also took an hour longer to reach home. What distance did he cover?
Options- A. 350 kms
- B. 450 kms
- C. 900 kms
- D. 700 kms Also asked in: AIEEE, Bank Exams, CAT, GATE, Analyst, Bank Clerk, Bank PO, Database Administrator, IT Trainer
Correct Answer: 900 kms
Explanation:
Let the distance he covered each way = d kms
According to the question,
d/45 - d/50 = 1
=> d = 450 kms.
Hence, the total distance he covered in his way = d + d = 2 d = 2 x 450 = 900 kms.
- 5. A Woman?s downstream swimming rate is thrice of her upstream swimming rate. If she covers 12 km upstream in 2.5 hours, what distance she will cover in 5 hours downstream?
Options- A. 72 km
- B. 36 km
- C. 56 km
- D. 42 km Also asked in: AIEEE, Bank Exams, CAT, GATE, Analyst, Bank Clerk, Bank PO
Correct Answer: 72 km
Explanation:
Rate of her upstream = 12/2.5 = 4.8 km/hr
Then, ATQ
Rate of downstream = 4.8 x 3 = 14.4 km/hr
Hence, the distance she covers downstream in 5 hrs = 14.4 x 5 = 72 kms.
- 6. A boat can move 5 km/hr in still water. If the river is running at 1 km/hr, it takes it 75 min to move to a place and back. How far is the place?
Options- A. 3 kms
- B. 5 kms
- C. 6 kms
- D. 4 kms Also asked in: AIEEE, Bank Exams, CAT, GATE, Analyst, Bank Clerk, Bank PO
Correct Answer: 3 kms
Explanation:
Let the place be at a distance of 'd' kms
From the given data,
5d/12 = 5/4 => d = 3 kms.
Hence, the place is 3 kms far.
- 7. A motorboat takes half time to cover a certain distance downstream than upstream. What is the ratio between rate of current and rate of boat in still water?
Options- A. 1 : 3
- B. 3 : 2
- C. 2 : 3
- D. 3 : 1 Also asked in: AIEEE, Bank Exams, CAT, GATE, Analyst, Bank Clerk, Bank PO, Database Administrator, IT Trainer
Correct Answer: 1 : 3
Explanation:
Let the speed of the boat in still water is 'w'
Speed of the current is 'c'
Let the distance between two places is 'd'
According to the question, motorboat takes half time to cover a certain distance downstream than upstream.
=> 2w - 2c = w + c
=> w = 3c
=> c : w = 1 : 3
Hence, the ratio between rate of current(c) and rate of boat in still water(w) = 1 : 3
- 8. A man can row upstream at 16 km/hr and downstream at 24 km/hr. Find the speed of the current.
Options- A. 4 kmph
- B. 6 kmph
- C. 5 kmph
- D. 3 kmph Also asked in: AIEEE, Bank Exams, CAT, GATE, Bank Clerk, Bank PO
Correct Answer: 4 kmph
Explanation:
Speed of the current = 24-16/2
= 8/2
= 4 km/hr.
- 9. A motorboat goes 8 km an hour in still water, but takes thrice as much time in going the same distance against the current than going with the current. Then find the speed of the current?
Options- A. 4 kmph
- B. 6 kmph
- C. 3 kmph
- D. 2 kmph Also asked in: GATE, CAT, Bank Exams, AIEEE, Bank PO, Bank Clerk, Analyst
Correct Answer: 4 kmph
Explanation:
Let the speed of current = 'C' km/hr
Given the speed of boat in still water = 6 kmph
Let 'd' kms be the distance it covers.
According to the given data,
Boat takes thrice as much time in going the same distance against the current than going with the current
i.e,
Hence, the speed of the current C = 4 kmph.
- 10. A boat while travelling upstream covers a distance of 29 km at the speed of 6 km/h, whereas while travelling downstream it covers the same distance at a speed of 12 km/h. What is the speed of the boat in still water?
Options- A. 6 kmph
- B. 8 kmph
- C. 9 kmph
- D. 11 kmph Also asked in: AIEEE, Bank Exams, CAT, GATE, Analyst, Bank Clerk, Bank PO
Correct Answer: 9 kmph
Explanation:
Speed of boat in still water = 1/2 (12 + 6) = 9 kmph.
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