1. A man swims downstream from one point to another which is 6 km apart in 1.5 hours. It covers the same distance upstream in 2 hours. Find the speed of the man in still water.
A) 4 kmph B) 4.1 kmph C) 4.2 kmph D) 3.5 kmph E) 4.5 kmph
2. A boat takes 8 hours to cover a distance while travelling upstream. Whereas while travelling downstream, it takes 6 hours, If the speed of the stream is 4 kmph, what is the speed of the boat in still water?
A) 16 kmph B) 18 kmph C) 28 kmph D) Cannot be determined E) None of these
Sol: Let the speed of the boat in still water be x kmph.
Then, (x + 4) × 6 = (x − 4) × 8
⇒ 6x + 24 = 8x − 32
x = 28 kmph.
3. A man takes to row 80 km along the stream is half of the time taken to row against the stream. Find the speed of the boat in still water if the speed of stream is 6 km/hr?
A) 24 km/hr B) 20 km/hr C) 18 km/hr D) 12 km/hr E) None of these
Sol: Let us take the speed of the boat in still water be x km/hr.
2x − 12 = x + 6 x = 18
Speed of the boat in still water = 18 km/hr
4. A boat running downstream covers a distance of 40 km in 5 hrs and for covering the same distance upstream, it takes 10 hrs. What is the speed of the stream?
A) 5 km/hr B) 2 km/hr C) 6 km/hr D) 4 km/hr E) 3 km/hr
5. A man takes thrice as long to row a distance against the stream as to row the same distance in favour of the stream. The ratio of the speed of the boat (in still water) and the stream is:
A) 2 : 1 B) 3 : 2 C) 1 : 2 D) 2 : 3 E) None of these
Sol: Speed of downstream : Speed of upstream = 3 : 1 (3x, x)
The ratio of speed of boat in still water and speed of stream is,
⇒ 2 : 1
6. A boat travels downstream for 14km and upstream for 9km. If the boat took total of 5 hours for its journey. What is the speed of the river flow if the speed of the boat in still water is 5km/hr?
A) 8km/hr B) 2km/hr C) 6km/hr D) 5km/hr E) 3km/hr
Sol: Let the speed of the stream be x km/hr Upward speed = (5 − x)km/hr Downward speed = (5 + x)km/hr According to the question,
⇒ (70 − 14x + 45 + 9x) / [(5 + x) (5 − x)] = 5
⇒ 115 − 5x = 125 − 5x2
⇒ 5x2 − 5x − 10 = 0
⇒ x2 − x − 2 = 0 ⇒ x = 2, −1(eliminate)
⇒ x = 2 km/hr
Speed of stream = 2 km/hr
7. Rajiv can swim at 10 km/hr in still water. The river flows at 3 km/hr and it takes 12 hours more upstream than downstream for the same distance. How far is the place?
A) 182 km B) 164 km C) 176 km D) 160 km E) 175 km
8. Mr. Suresh can row to a place 48 km away and come 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?
A) 1 kmph B) 3 kmph C) 4 kmph D) 6 kmph E) None of these
9. A Boat going upstream takes 8 hours 24 minutes to cover a certain distance, while it takes 5 hours to cover 5/7 of the same distance running downstream. Then what is the ratio of the speed of boat to speed of water current?
A) 6 : 5 B) 11 : 5 C) 11 : 6 D) 11 : 1 E) 11 : 10
S : R = 11 : 1
10. Mr. Ramesh’s speed with the current is 20 kmph and the speed of the current is 5 kmph. Ramesh’s speed against the current is?
A) 15 kmph B) 19 kmph C) 17 kmph D) 10 kmph E) None of these
Sol: Ramesh’s speed with the current = 20 kmph
⇒ Ramesh’s speed = 20 − 5 = 15 kmph Ramesh’s speed against the current
= speed of Ramesh − speed of the current
= 15 − 5 = 10 kmph
11. A Boat takes total 16 hours for travelling downstream from point A to point B and coming back point C which is somewhere between A and B. If the speed of the Boat in Still water is 9 Km/hr and rate of stream is 6 Km/hr, then what is the distance between A and C?
A) 30 Km B) 60 Km C) 90 Km D) 100 Km E) Cannot be determined
12. Ravi can row 12 kmph in still water when the river is running at 6 kmph it takes him 1 hour to row to a place and to come back. How far is the place?
A) 5.5 km B) 4.5 km C) 8.2 km D) 4.2 km E) None of these
Sol: Downstream Speed = 18 kmph
Upstream Speed = 6 kmph
Distance = x
x = 4.5 km
13. The different between downstream speed and upstream speed is 2 kmph and the total time taken during upstream and downstream is 2 hours. What is the upstream speed, if the downstream and upstream distance are 2 km each?
A) 5.2 kmph B) 3.7 kmph C) 2.8 kmph D) 1.4 kmph E) None of these
x2 − 2 = 0
x = 1.414kmph
14. A Boat took 8 hours less to travel a distance downstream than to travel the same distance upstream. If the speed of a boat in still water is 9 Km/hr and speed of a stream is 3 Km/hr. In total how much distance travelled by boat?
A) 96 Km B) 144 Km C)164 Km D) 192 Km E) 216 Km
Total = 96 + 96 = 192
15. A boat running downstream covers 28 kms in 7 hours, while for covering the same distance upstream it takes 4 hours. What is the speed of the boat in still water?
A) 4 km/hr B) 4.5 km/hr C) 5 km/hr D) 5.5 km/hr E) None of these
16. In a stream, B lies in between A and C such that it is equidistant from both A and C)A boat can go from A to B and back in 6 h 30 minutes while it goes from A to C in 9 h. How long would it take to go from C to A?
A) 2 h B) 4.5 h C) 4 h D) 3.5 h E) None of these
Sol: Time taken to go form A to B = Time taken to go from A to C/2
Time taken to go from B to A = 6.5 − 4.5 = 2
hours Time taken to go from C to A = 2 × 2 = 4 hours