Boats and Streams Questions

Q:

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 ?

A) 1.78 kmph B) 2.35 kmph
C) 2.83 kmph D) 3.15 kmph
 
Answer & Explanation Answer: C) 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.

Report Error

View Answer Report Error Discuss

Filed Under: Boats and Streams
Exam Prep: AIEEE , Bank Exams , CAT , GATE
Job Role: Bank Clerk , Bank PO

14 5870
Q:

Rajesh rows in still water with a speed of 4.5 kmph to go to a certain place and comes back. Find his average speed for the whole journey, if the river is flowing with a speed of 1.5 kmph?

A) 2 kmph B) 4 kmph
C) 6 kmph D) 8 kmph
 
Answer & Explanation Answer: B) 4 kmph

Explanation:

Let the distance in one direction = k kms

Speed in still water = 4.5 kmph

Speed of river = 1.5

Hence, speed in upstream = 4.5 - 1.5 = 3 kmph

Speed in downstream = 4.5 + 1.5 = 6 kmph

Time taken by Rajesh to row upwards = k/3 hrs

Time taken by Rajesh to row downwards = k/6 hrs

Now, required Average speed =Total distanceTotal speed = 2kk3 + k6 = 2k x 186k + 3k = 4 kmph 

 

Therefore, the average speed of the whole journey = 4kmph.

Report Error

View Answer Report Error Discuss

19 5861
Q:

A motorboat can go 10 miles downstream on a river in 20 min. It takes 30 min for this boat to go back at the same 10 miles. Find the speed of the current ?

A) 8 m/h B) 5 m/h
C) 7 m/h D) 6 m/h
 
Answer & Explanation Answer: B) 5 m/h

Explanation:

As the distance travelled is constant, the time taken is inversely proportional to speed.

Let 'u' be the speed of the current and 'v' be the speed of the boat.

Speed of the boat downstream = v + u & upstream = v - u

=> v+u/v-u = 30/20 => v/u = 5 => v = 5u

=> v + u = 6u = 10/20/60 miles/hr

=> 6u = 30 m/h

=> u = 5 m/h

Report Error

View Answer Report Error Discuss

Filed Under: Boats and Streams
Exam Prep: AIEEE , Bank Exams , CAT , GATE
Job Role: Bank Clerk , Bank PO

20 5449
Q:

A boat takes 2 hours to travel from point A to B in still water. To find out its speed upstream, which of the following information is/are required?

A. Distance between point A and B.

B. Time taken to travel downstream from B to A.

C. Speed of the stream of water.

A) Only A and B B) Only B and C
C) All are required D) Any one pair of A and B, B and C or C and A is sufficient
 
Answer & Explanation Answer: D) Any one pair of A and B, B and C or C and A is sufficient

Explanation:

Let distance between A & B = d km
Let speed in still water = x kmph
Let speed of current = y kmph

from the given data,
d/x = 2

From A) we get d
From B) we get d/x+y
From C) we get y

 

So, Any one pair of A and B, B and C or C and A is sufficient to give the answer i.e, the speed of upstream.

Report Error

View Answer Report Error Discuss

Filed Under: Boats and Streams
Exam Prep: AIEEE , Bank Exams , CAT , GATE
Job Role: Analyst , Bank Clerk , Bank PO

7 5240
Q:

 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?

A) 1 : 3 B) 3 : 2
C) 2 : 3 D) 3 : 1
 
Answer & Explanation Answer: A) 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.

dw+c = 12dw-c

=> 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

Report Error

View Answer Report Error Discuss

12 4770
Q:

If the boat goes 7 kms upstream in 42 min and speed of the stream is 3 kmph, then the speed of the boat in still water ?

A) 14 kmph B) 13 kmph
C) 12 kmph D) 11 kmph
 
Answer & Explanation Answer: B) 13 kmph

Explanation:

Given that, upstream distance = 7 kms

Upstream speed = 7/42 x 60 = 10 kms

Speed of the stream = 3 kmph

Let speed in still water = M kmph, then

Upstream speed = M - 3 = 10

=> M = 13 kmph.

Report Error

View Answer Report Error Discuss

Filed Under: Boats and Streams
Exam Prep: AIEEE , Bank Exams , CAT , GATE
Job Role: Analyst , Bank Clerk , Bank PO

10 4704
Q:

Find the speed of stream if a boat covers 36 km in downstream in 6 hours which is 3 hours less in covering the same distance in upstream?

A) 1.5 kmph B) 1 kmph
C) 0.75 kmph D) 0.5 kmph
 
Answer & Explanation Answer: B) 1 kmph

Explanation:

Speed of the boat upstream = 36/9 = 4 kmph

Speed of the boat in downstream = 36/6 = 6 kmph

Speed of stream = 6-4/2 = 1 kmph

Report Error

View Answer Report Error Discuss

18 4059
Q:

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?

 

A) 72 km B) 36 km
C) 56 km D) 42 km
 
Answer & Explanation Answer: A) 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.

Report Error

View Answer Report Error Discuss

Filed Under: Boats and Streams
Exam Prep: AIEEE , Bank Exams , CAT , GATE
Job Role: Analyst , Bank Clerk , Bank PO

17 3787