Boats and Streams - Quantitative Aptitude (MCQ) questions

1)   The speed of boat in still water is 20 km/hr. If it travels 26 km downstream and 14 km upstream in same time, what is the speed of the stream?
- Published on 06 May 16

a. 4 km/hr
b. 5 km/hr
c. 6 km/hr
d. 7 km/hr
Answer  Explanation 

ANSWER: 6 km/hr

Explanation:
Let X be speed of stream
Speed of boat downstream = (20 + X )
Speed of boat upstream = (20 – X)
It is given that boat takes same time to travel 26 km downstream and 14 km upstream
[26/(20 +X)] = [14 / (20 – X)]
520 – 26 X = 280 + 14X
40X = 240
X = 6 km/hr


2)   A boat running downstream covers a distance of 20 km in 2 hours while for covering the same distance upstream, it takes 5 hours. What is the speed of the boat in still water?
- Published on 06 Apr 16

a. 4 km / hr
b. 7 km / hr
c. 8 km / hr
d. Data Inadequate
Answer  Explanation 

ANSWER: 7 km / hr

Explanation:
Rate downstream = (20/2) kmph = 10 kmph;
Rate upstream = (20/5) kmph = 4 kmph
Speed in still water = 1/2 (10 + 4) kmph = 7 kmph


3)   The speed of a boat in still water is 20 km/hr and the rate of current is 5 km/hr. The distance travelled downstream in 12 minutes is:
- Published on 28 Mar 16

a. 1.8 km
b. 7 km
c. 5 km
d. 3 km
Answer  Explanation 

ANSWER: 5 km

Explanation:
Speed downstream = (20+5) kmph = 25 kmph
Distance travelled = (25*(12/60)) km = 5 km.


4)   A boats man can row in still water at speed of 7 km/hr. It takes 6 hours more to travel the same distance in upstream than in downstream if the speed of the river is 3 km/hr. what is the distance between the two destinations?

- Published on 06 Jul 15

a. 20 km
b. 40 km
c. 30 km
d. 10 km
Answer  Explanation 

ANSWER: 40 km

Explanation:
x = 7 km/hr ; y = 3 km/hr
Ds = 10 km/hr ; Us = 4 km/hr
Distance (d) is same. Therefore, if time taken for downstream is t hours, the time for upstream is (t + 6) hours.
10*t = 4*(t + 6)
6t = 24 ; t = 4 hours
d = 10*4 = 40 km


5)   If a boat is rowed downstream for 50 km in 5 hours and upstream for 24 km in 6 hours, what is the speed of the boat and the river?
- Published on 06 Jul 15

a. (7 , 3) km/hr
b. (6 , 4) km/hr
c. (10 , 4) km/hr
d. None of these
Answer  Explanation 

ANSWER: (7 , 3) km/hr

Explanation:
If x: speed of boats man in still water
y: speed of the river
Downstream speed (Ds) = x + y
Upstream speed (Us) = x – y
x = (Ds + Us) / 2
y = (Ds – Us) / 2
In the above problem Ds = 10 ; Us = 4
x = (10 + 4) / 2 = 14/2 = 7 km/hr
y = (10 - 4)/2 = 6/2 = 3 km/hr


6)   A man can row a boat three quarters of a kilometre in 11.25 minutes. What is the speed of the boat in still water?
- Published on 12 Jun 15

a. 2 kmph
b. 5 kmph
c. 4 kmph
d. 3 kmph
Answer  Explanation 

ANSWER: 4 kmph

Explanation:
Simple Division.
No stream current mentioned.
Trick question.
Speed= Distance/Time.
Speed= 3/4 km / (11.25/60) hr
Therefore, Speed = 4 km/hr


7)   A boatman rows 96 km downstream in 8 hours with a stream speed of 4kmph. How much time will he take to cover 8km upstream?
- Published on 12 Jun 15

a. 4 hours
b. 6 hour
c. 2 hours
d. 1 hours
Answer  Explanation 

ANSWER: 2 hours

Explanation:
Speed = distance/time

Speed downstream: 96 / 8 km/hr = 12kmph

Speed of stream = 4kmph

Effective speed of boat = (12-4) kmph
= 8kmph

Distance to be travelled upstream= 8 km

Speed upstream = boat speed-current speed

= 8-4 kmph

= 4 kmph

Time taken = distance/speed = 8/ 4 hours
=2 hours

Thus it will take 2 hours to go upstream.


8)   A boat with speed 15 km/hr in standing water goes 30 km downstream and returns in a total of 4.5 hours. What is the speed of current?
- Published on 12 Jun 15

a. 4 kmph
b. 6 kmph
c. 5 kmph
d. 8 kmph
Answer  Explanation 

ANSWER: 5 kmph

Explanation:
Speed of the boat in still water: 15 km/hr

Speed of boat downstream: (15+x)km/hr where x is speed of the current.

The boat travels 30 km downstream and then 30 km upstream and takes 9/2 hours.

Total time= Time taken to travel downstream + Time taken to travel upstream

=> 4/5= (30/(15+x))+(30/(15-x))

=>x= 5


9)   A boat has a speed of 14kmph in standing water. The stream has a speed of 1.2kmph. What time does the boat take to go to a distance of 4864 km and come back? (hours)
- Published on 19 Oct 15

a. 700
b. 350
c. 1000
d. 4200
Answer  Explanation 

ANSWER: 700

Explanation:
A boat travels at the speed of 14 km/hr in still water.

=> Speed of stream = 1.2 kmph

=> Speed of boat downstream becomes 14 + 1.2 = 15.2 kmph

=> Speed of boat upstream becomes 14 - 1.2 = 12.8 kmph

Total time taken in the journey = Journey downstream + Journey upstream

Therefore, 4864(1/12.8 + 1/15.2) = 700 hours


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