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01. The rate of a stream is 4 kmph. A boat goes 6 km and back to the starting point in 2 hours. What is the speed of the boat in still water?
A. 3 kmph B. 4 kmph
C. 10 kmph D. 8 kmph

Answer and Explanation

Answer: 8 kmph

Explanation:
Let the speed of the boat in still water be x kmph.
=> Speed downstream = (x + 4) kmph, Speed upstream = (x – 4) kmph
=> Time taken to go 6 km downstream = 6/(x -4), time taken to go
=> 6 km upstream = 6/(x – 4) * 6/(x +4) + 6/ (x – 4) = 2 hours.
Solving the equations x = 8

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02. A man can row upstream at 8 kmph and downstream at 13 kmph. The speed of the stream is
A. 2.5 kmph B. 4.2 kmph
C. 5 kmph D. 10.5 kmph

Answer and Explanation

Answer: 2.5 kmph

Explanation:
Speed of the stream = ½ (13 – 8) kmph = 2.5 kmph

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03. Anand can row 20 km in 2 hours in still water. If the speed of the stream is 6 kmph, he would take 3.75 hours to cover a round trip journey. Find the distance that he would then cover each way.
A. 11 B. 12
C. 15 D. 16

Answer and Explanation

Answer: 12

Explanation:
Speed of the boat in still water = 20/2 = 10 kmph
=> Let the total distance covered be 2x km
=> Given that, x/10+6 + x/10-6 = 3.75
x = 12

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04. Anand can row a boat in still water at a speed of 5 kmph. The speed of the stream is 3 kmph. Find the time taken by him to row 40 km downstream (in hours).
A. 5 B. 20
C. 8 D. 15

Answer and Explanation

Answer: 5

Explanation:
Speed of Anand’s boat downstream = 8 kmph
Time taken = 40/8 = 5 hours.

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05. A man rows at the rate of 5 kmph in still water. If the river runs at the rate of 1.5 kmph, it takes him 1 hour to row to a place and back. What is the distance?
A. 2 km 275 m B. 3 km 275m
C. 5 km 100 m D. 3 km 280 m

Answer and Explanation

Answer: 2 km 275 m

Explanation:
Man’s rate downstream = (5 + 1.5) kmph = 6.5 kmph
=> Man’s rate upstream = (5 – 1.5) kmph = 3.5 kmph
=> Let the distance be x km
=> Total time taken to row x km and back
=> = (x / 6.5 + x / 3.5) = 1
=> x = 2.275 km
thus the distance = 2 km 275 m

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06. In one hour, A boat goes 11 kms along the stream and 5 kms against the stream. The speed of the boat in still water is
A. 3 kmph B. 5 kmph
C. 8 kmph D. 6 kmph

Answer and Explanation

Answer: 8 kmph

Explanation:
Speed in still water = ½ (11 + 5) = 8 kmph

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07. In a certain time, a boat can cover either a certain distance upstream or 5/2 times that distance downstream. If the speed of the current is 6 kmph, find the speed of the boat in still water.
A. 20 B. 14
C. 16 D. 22

Answer and Explanation

Answer: 14

Explanation:
Let the speed of the boat in still water be x kmph.
=> X+6 / x-6 = 5/2
=> 2x + 12 = 5x – 30
x = 14

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08. A boat running downstream covers a distance of 16 kms in 2 hrs while for covering the same distance upstream, it takes 4 hrs. What is the speed of the boat in still water?
A. 4 kmph B. 6 kmph
C. 8 kmph D. Data inadequate

Answer and Explanation

Answer: 6 kmph

Explanation:
Rate downstream = 16/2 kmph = 8 kmph ; Rate upstream = 16/4 kmph = 4 kmph
Hence, Speed in still water = ½ (8 + 4) kmph = 6 kmph

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09. A person rows a kilometer down the stream in 10 minutes and up the stream in 30 minutes. Find the velocity of the stream.
A. 1 kmph B. 2 kmph
C. 5 kmph D. 3kmph

Answer and Explanation

Answer: 2 kmph

Explanation:
Let the speed upstream and speed downstream be Su and Sd respectively
=> Su = (1000/30)(1/60) = 5/9 m/s
=> Sd = (1000/10) (1/60) = 5/3 m/s
=> Let the speed of the boat and the current be x m/s and y m/s respectively
=> x + y = 5/3
=> x – y = 5/9
=> Solving these two equations simultaneously,
=> y = 5/9 m/s = 5/9 (3600 / 1000) = 2 kmph
The speed of the current = 2 kmph

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10. A boat man goes 2 kms against the current of the stream in1 hour and goes 1 km along the current in 10 mins. How long will it take to go 5 km in stationary water?
A. 40 mins B. 1 hr
C. 1 hr 15 mins D. 50 mins

Answer and Explanation

Answer: 1 hr 15 mins

Explanation:
Rate downstream = (1/10 * 60) kmph = 6 kmph, Rate Upstream = 2 kmph
Speed in still water = ½ (6 + 2) kmph = 4 kmph
Hence, Required time = 5/4 hrs = 1 ¼ hours = 1 hr 15 mins

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