Latest Capgemini Aptitude Question SOLUTION: A river runs at 4 km/hr. if the time taken by a man to row is boat upstream is 3 as the time taken by him to row it downstream then find the speed of the boat in still water.

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A river runs at 4 km/hr. if the time taken by a man to row is boat upstream is 3 as the time taken by him to row it downstream then find the speed of the boat in still water.

Asked In Capgemini krutika mishra (10 years ago)

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azharshahid01@gmail.com  (10 years ago)

If the speed upstream is x km/hr and the speed downstream is 3x km/hr, then:
Speed in still water = (1/2)*(x+3x) km/hr.

Rate of stream = (1/2)*(3x-x) km/hr.
So 4= (1/2)*2x; => x= 4.

Thus, speed in still water= (1/2)*(4+12) => 16/2 => 8.
So, Speed of boat in still water is 8 km/hr.

Is this solution Helpfull? Yes (28) | No (1)  

Naresh Jain  (9 years ago)

Speed(upstream)=Speed(Boat)- Speed(River)
Speed(downstream)=Speed(Boat)+ Speed(River)

Given is if x is speed at downstream then 3x is speed at upstream
speed(River)=4

Substitute the values in Above eqn.
x=Speed(Boat)+4
3x=Speed(Boat)-4

Multiply firs eqn by 3 and sub both.

speed(boat)=8kmph.

Is this solution Helpfull? Yes (11) | No (2)  

D Kiran Kumar  (10 years ago)

Time(Upstream)=3T(Downstream)
d/x-y=3(d/x+y)
x+y=3x-3y
4y=2x
x=2y
x=8Kmph

Is this solution Helpfull? Yes (6) | No (2)  

raviteja  (10 years ago)

sry its 3(x-4)=x+4

Is this solution Helpfull? Yes (4) | No   

Niteesh  (10 years ago)

Now here let distance is same (Not mentioned) & time is inversely varies as speed=distane/time,
so speed so solve in the following way
let the rate in still wtr be x kmph,
upstream x+4, dwnstream x-4,

comparing speeds 3(x-4) = (x+3)
3+y=6-3y
y=1.5 is the correct answer

Is this solution Helpfull? Yes (3) | No (6)  

raviteja  (10 years ago)

let the rate in still wtr be x kmph,
upstream x+4, dwnstream x-4, comparing speeds (x-4) = 3(x+3)
gives 8kmph

Is this solution Helpfull? Yes (2) | No   

swetha.Gunda  (10 years ago)

plz,explain clearly @ RAVITEJA

Is this solution Helpfull? Yes (1) | No   

Mohan Reddy  (9 years ago)

Assume that he moves 4 km downstream in x hours

Then, speed downstream = distance time= 4x km/hr

Given that he can row 4 km with the stream in the same time as 3 km against the stream

i.e., speed upstream = 3/4 of speed downstream
speed upstream = 3x km/hr

He rows to a place 48 km distant and come back in 14 hours

=>48/(4x)+48/(3x)=14
=>12/x+16/x=14
=>6x+8x=7
=>14x=7
=>x=1/2
Hence, speed downstream = 4x = 4(1/2) = 8 km/hr
speed upstream = 3x=3(1/2) = 6 km/hr

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raviteja  (10 years ago)

still water boat speed 8kmph

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rajiv  (10 years ago)

8
bec. put t=3t u will get d answer

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vinitha bangaru  (10 years ago)

azhar shahid.. why u r taken 1/2 * (3x-x) = 4 he z not mentioned dat it is a upstream.. plz explain clearly..

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nk gour  (9 years ago)

speed of water = 4kmph
upstream speed= 3kmph
then downstream will be
speed of water= (downstream speed- upstream speed)/2
4=DS-3/2
DS-3=8
Ds=11
so speed in still water will be=Ds-SOW
= 11-4
=7
or speed in still water will be= US+SOW
=3+4
=7 ans.

Is this solution Helpfull? Yes | No (1)  

huma afreen  (6 years ago)

speed of current=4 km/hr time taken upstream=3t and time taken downstream=t
speed upstream=d/3t and speed downstream=d/t
speed of current=1/2(d-u); 4=1/2(d/t +d/3t) so 12=d/t
so upstream speed=12/3=4 km/hr downstream=12 km/hr
now finding speed of boat=1/2(d+u)=>1/2*16=>8 km/hr (ans)

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Pratyusha Trivedi  (3 years ago)

Let Speed of Boat = B km/hr and Distance = x km
Speed of River (R) = 4 km/hr
Speed Upstream = (B+R) km/h
Speed Downstream = (B-R) km/h

Now,
Time Upstream = 3 (Time Downstream)
x/B-R = 3*(x/B+R) ------------------------------ [Time = Distance/Speed]

x/B-R = 3x/B+R
1/B-R = 3/B+R
B+4 = 3B - 12 ------------------------------[since R=4 km/h]
2B = 16
B = 8 km/hr

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