BOATS & STREAMS – Aptitude Interview Questions with Answers 

This blog explains about BOATS & STREAMS – Aptitude Interview Questions with Answers and is given below : 

1.    A man can row at 5 kmph in still water. If the velocity of current is 1 kmph and it takes him 1 hour to row to a place and come back, how far is the place?
A 2.4 km
B 2.5 km
C 3 km
D 3.6 km

Answer: Option A

Explanation:

Speed downstream = (5 + 1) kmph = 6 kmph.

Speed upstream = (5 – 1) kmph = 4 kmph.

Let the required distance be x km.

Then, x + x = 1
6 4

 2x + 3x = 12

 5x = 12

 x = 2.4 km.

 

 

 2 . A boatman goes 2 km against the current of the stream in 1 hour and goes 1 km along the current in 10 minutes. How long will it take to go 5 km in stationary water?
A 40 minutes
B 1 hour
C 1 hr 15 min
D 1 hr 30 min

Answer: Option C

Explanation:

Rate downstream =   1 x 60 km/hr = 6 km/hr.
10

Rate upstream = 2 km/hr.

Speed in still water = 1 (6 + 2) km/hr = 4 km/hr.
2

 

 Required time =   5 hrs = 1 1 hrs = 1 hr 15 min.
4 4

 

 3 . A man rows to a place 48 km distant 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 km/hr
B 1.5 km/hr
C 2 km/hr
D 2.5 km/hr
 

Answer: Option A

Explanation:

Suppose he move 4 km downstream in x hours. Then,

Speed downstream =   4   km/hr.
x

 

Speed upstream =   3   km/hr.
x

 

  48 + 48 = 14 or x = 1 .
(4/x) (3/x) 2

So, Speed downstream = 8 km/hr, Speed upstream = 6 km/hr.

Rate of the stream = 1 (8 – 6) km/hr = 1 km/hr.
2

 4 . A man’s speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man’s speed against the current is:

A 8.5 km/hr
B 9 km/hr
C 10 km/hr
D 12.5 km/hr

 

Answer: Option C

Explanation:

Man’s rate in still water = (15 – 2.5) km/hr = 12.5 km/hr.

Man’s rate against the current = (12.5 – 2.5) km/hr = 10 km/hr.

 

 5 . A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is:
A 4
B 5
C 6
D 10

Answer: Option B

Explanation:

Let the speed of the stream be x km/hr. Then,

Speed downstream = (15 + x) km/hr,

Speed upstream = (15 – x) km/hr.

  30 + 30 = 4 1
(15 + x) (15 – x) 2

 

  900 = 9
225 – x2 2

 9x2 = 225

 x2 = 25

 x = 5 km/hr.

 

 

 6 . A boat 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 boat and speed of the water current respectively?
A 2 : 1
B 3 : 2
C 8 : 3
D Cannot be determined
E None of these

Answer: Option C

Explanation:

Let the man’s rate upstream be x kmph and that downstream be y kmph.

Then, distance covered upstream in 8 hrs 48 min = Distance covered downstream in 4 hrs.

    x x 8 4   = (y x 4)
5

 

  44 x =4y
5

 

 y = 11 x.
5

 

 Required ratio =   y + x   :   y – x  
2 2

 

   =   16x x 1   :   6x x 1  
5 2 5 2

 

   = 8 : 3
5 5

   = 8 : 3.

 

 7 .In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is:
A 3 km/hr
B 5 km/hr
C 8 km/hr
D 9 km/hr

Answer: Option C

Explanation:

Speed in still water = 1 (11 + 5) kmph = 8 kmph.
 

 

 8 . A boat running downstream covers a distance of 16 km in 2 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 6 km/hr
C 8 km/hr
D Data inadequate

Answer: Option B

Explanation:

Rate downstream =   16 kmph = 8 kmph.
2

 

Rate upstream =   16 kmph = 4 kmph.
4

 

 Speed in still water = 1 (8 + 4) kmph = 6 kmph.
2

 

 9 .The speed of a boat in still water in 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is:
A 1.2 km
B 1.8 km
C 2.4 km
D 3.6 km

Answer: Option D

Explanation:

Speed downstream = (15 + 3) kmph = 18 kmph.

Distance travelled =   18 x 12 km = 3.6 km.
60

 

 10 . A boat covers a certain distance downstream in 1 hour, while it comes back in 1 hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water?
A 12 kmph
B 13 kmph
C 14 kmph
D 15 kmph
E None of these

Answer: Option D

Explanation:

Let the speed of the boat in still water be x kmph. Then,

Speed downstream = (x + 3) kmph,

Speed upstream = (x – 3) kmph.

 (x + 3) x 1 = (x – 3) x 3
2

 2x + 6 = 3x – 9

 x = 15 kmph.