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- Question
- The speed of a boat in still water is 4 km/hr and the speed of current is 2 km/hr. If the time taken to reach a certain distance upstream is 9 hours, find the time it will take to go same distance downstream?
Options- A. 2 hrs
- B. 2.5 hrs
- C. 3.5 hrs
- D. 3 hrs
- Correct Answer
- 3 hrs
ExplanationUpstream distance = (4 - 2) x 9 = 18 km
? Required time = 18/(4 + 2) = 3 hrs. - 1. A motorboat travelling at the same speed, can cover 25 km upstream and 39 km downstream in 8 h. At the same speed, it can travel 35 km upstream and 52 km downstream in 11 h. The speed of the stream is?
Options- A. 2 km/h
- B. 3 km/h
- C. 4 km/h
- D. 5 km/h Discuss
- 2. A boat running upstream takes 528 min to cover a certain distance, while it takes 240 min to cover the same distance running downstream. What is the ratio between the speed of the water current, respectively?
Options- A. 2 : 1
- B. 3 : 2
- C. 8 : 3
- D. Couldn't be determined Discuss
- 3. A man can row against the current three-fourth of a kilometre in 15 min and returns same distance in 10 min, then ratio of his speed to that of current is?
Options- A. 3 : 5
- B. 5 : 3
- C. 1 : 5
- D. 5 : 1 Discuss
- 4. In a river, the ratio of the speed of stream and speed of a boat in still water is 2 : 5 Again, ratio of the speed of stream and speed of an another boat in still water is 3 : 4. What is the ratio of the speeds of the first boat to the second boat in still water?
Options- A. 10 : 7
- B. 15 : 8
- C. 4 : 3
- D. 5 : 4 Discuss
- 5. A steamer goes downstream from one port to another in 4 h. It covers the same distance upstream in 5 h. If the speed of the stream is 2 km/h, then find the distance between the two ports.?
Options- A. 50 km
- B. 60 km
- C. 70 km
- D. 80 km Discuss
- 6. Ramesh can row a certain distance downstream is 6 hours and return the same distance in 9 hours. If the speed of Ram, Ramesh in still water is 12 km/hr, find the speed of the stream.
Options- A. 2.4 km/hr
- B. 2 km/hr
- C. 3 km/hr
- D. Data inadequate Discuss
- 7. A man rows to a place 48 km distance 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. Find the rate of the stream?
Options- A. 1 km/hr
- B. 2 km/hr
- C. 1.5 km/hr
- D. 2.5 km/hr Discuss
- 8. Raman covers 1 km in 8 min while suman covers the same distance in 10 min. By what distance does Raman beat Suman?
Options- A. 150 m
- B. 65 m
- C. 190 m
- D. 200 m Discuss
- 9. In a race of 150 m, A gives B a start of 20 m. What distance will be covered by B?
Options- A. 100 m
- B. 130 m
- C. 170 m
- D. 160 m Discuss
- 10. In a race, P gives Q a start of 25 m making length of race for Q a distance of 175 m. Find the total length of race.?
Options- A. 250 m
- B. 200 m
- C. 225 m
- D. 235 m Discuss
Boats and Streams problems
Search Results
Correct Answer: 4 km/h
Explanation:
Let the speed of a boat and stream be U and V km/h
? Speed of boat along stream = (U + V) km/h
and speed of boat against stream = (U - V) km/h
According to the question,
25/(U - V) + 39/(U + V) = 8 ....(i)
and 35/(U - V) + 52/(U + V ) = 11 ..(ii)
On multiplying Eq. (i) by 4 and Eq. (ii) by 3, then subtract Eq. (ii) from Eq, we get
100/(U - V) - 105/(U - V) = -1
? 5/(U - V) = 1
? U - V = 5 ...(iii)
On substituting the value of (U - V) = 5 in Eq. (i) we get
25/5 + 39/(U + V) = 8
? 39/(U + V) = 8 - 5
? U + V = 39/3
? U + V = 13 ....(iv)
On solving Eqs. (iii) and (iv), we get
U = 9 and V = 4
Hence, speed of stream = 4 km/h
Correct Answer: 8 : 3
Explanation:
Let boat's rate upstream be U and boat's rate downstream = V
According to the question.
Distance covered in 528 min = Distance covered in 240 min
? Distance covered in 8 h 48 min = Distance covered in 4 h
? U x 84/5 = V x 4
? (44 x U)/5 = 4V
? V = (11 x U)/5
? Required ratio = (V + U)/2 : (V - U)/2
? = (11U/5 + U)/2 : (11U/5 - U)/ 2
? = 16U/5 : 6U/5 = 8 : 3
Correct Answer: 5 : 1
Explanation:
Let the speed of man and current be U and V km/h, respectively.
Speed upstream = (U - V) km/h
Speed down stream = (U + V) km/h
According to the question,
(3 x 60)/(4 x 15) = U - V
? U - V = 3 ......(i)
and (3/4) x (60/10) = U + V
? U + V = 9/2 ...(ii)
On adding Eqs. (i) and (ii), we get
2U = 3 + 9/2
? U = 15/4
On putting the value of U in Eq. (ii), we get
15/4 + V = 9/2
V = 9/2 - 15/4 = 18 - 15/4
? V = 3/4
Hence, speed of man U = 15/4 and
Speed of current V = 3/4
Hence, required ratio = 15/4 : 3/4 = 5 : 1
Correct Answer: 15 : 8
Explanation:
For the first boat,
Speed of stream : Speed of boat = 2: 5
Let speed of stream be 2x km/h and speed of boat = 5x km/h
Similarly, for the second boat
Speed of stream be 3y km/h and speed of boat = 4y
In both of the conditions, river is same.
? 2x = 3y
? x = 3y/2
Thus, required ratio in speeds of boats in still water
= Thus, required ratio in speeds of boats in still water
= 5x : 4y = (5 x 3)y/2 : 4y = 15 : 8
Correct Answer: 80 km
Explanation:
Let the distance between the two ports be x km.
Then, speed downstream = x/4
And speed upstream = x/5
? Speed of the stream = [speed downstream + speed upstream] / 2 = (x/4 - x/5)/2
? (5x -4x)/40 = 2
? x/40 = 2
? x = 80 km
Correct Answer: 2.4 km/hr
Explanation:
? [(9 + 6)/(9 - 6)] x v = 12
? v = 2.4 km/hr
Correct Answer: 1 km/hr
Explanation:
Suppose that the man takes H hours to cover 4 km downstream and H house to cover 3 km upstream.
Then, 48H/4 + 48H/3 = 14
? H = 1/2
? Rate upstream = 3/(1/2)= 6 km/hr
and rate downstream = 4/(1/2) = 8 km/hr
? Rate of the stream = (8 - 6)/2 = 1 km/hr .
Correct Answer: 200 m
Explanation:
Raman covers 1 km in 8 min
and suman cover 1 km in 10 min.
If they starts together, then distance covered by suman in 8 min
= (1000/10) x 8 = 800 m
? Raman will beat suman by (1000 - 800 ) m = 200 m
Correct Answer: 130 m
Explanation:
Required distance = (150 - 20) m = 130 m
Correct Answer: 200 m
Explanation:
Required length = (175 + 25)m = 200 m
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