Aptitude - Boats and Streams - Discussion
Discussion Forum : Boats and Streams - General Questions (Q.No. 3)
3.
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?
Answer: Option
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.
Discussion:
109 comments Page 3 of 11.
Ganesha (lecturer) said:
1 decade ago
You are excellent @Aparna, @Mady you too. Both are right is solving this but we have to go still easier and a shortcut method to solve why because is we can't waste 10 mins for a single aptitude in the examinations, which may lead to shortage of time.
Great job appreciative but still try best don't settle for good.
Great job appreciative but still try best don't settle for good.
Sekhar said:
8 years ago
The speed of the boat = 1/2(up stream + downstream) speed of the current = 1/2(up stream - downstream).
converting 8 hours 48 minutes to minutes which is 528 minutes.
converting 4 hours to minutes which is 240 minutes.
1/2(528+240) : 1/2(528-240).
1/2 on both sides gets canceled so,
768 : 288 ==> 8: 3.
converting 8 hours 48 minutes to minutes which is 528 minutes.
converting 4 hours to minutes which is 240 minutes.
1/2(528+240) : 1/2(528-240).
1/2 on both sides gets canceled so,
768 : 288 ==> 8: 3.
Shifali said:
6 years ago
Let the speed of the boat is u and that of the stream is v.
Time for upstream (u-v) is 528min and time took for downstream (u+v) is 240 min.
Distance covered is the same.
Since, D1=t1*(u-v) and d2= t2*(u+v).
And, d1=d2
So, t1*(u-v) = t2*(u+v).
(U-v)*528 = (u+v)*240
=> u/v = 8/3;
That is 8:3.
Time for upstream (u-v) is 528min and time took for downstream (u+v) is 240 min.
Distance covered is the same.
Since, D1=t1*(u-v) and d2= t2*(u+v).
And, d1=d2
So, t1*(u-v) = t2*(u+v).
(U-v)*528 = (u+v)*240
=> u/v = 8/3;
That is 8:3.
Mady said:
1 decade ago
Boat Speed In still water = u.
Stream Speed = v.
DS = u+v US = u-v.
Distance = (u+v)4 = (u-v)44/5 (rough : 8*48/60= 44/5).
so (u+v) = (u-v)11/5 (rough : canceled 4 & 44.. 11 times).
5(u+v) = (u-v)11.
5u+5v = 11u-11v.
5u-11u = -11v-5v.
-6u = -16v.
u/v = 16/6= 8/3 .
So 8:3.
Stream Speed = v.
DS = u+v US = u-v.
Distance = (u+v)4 = (u-v)44/5 (rough : 8*48/60= 44/5).
so (u+v) = (u-v)11/5 (rough : canceled 4 & 44.. 11 times).
5(u+v) = (u-v)11.
5u+5v = 11u-11v.
5u-11u = -11v-5v.
-6u = -16v.
u/v = 16/6= 8/3 .
So 8:3.
SAGOR said:
7 years ago
Let, the distance be = d.
Downsream speed= d/4,
Upstream speed= 5d/44,
So, d/4 : 5d/44.
11: 5.
Now, the speed of the boat =(11+5)/2.
= 8.
The speed of the current =(11-5)/2.
= 3.
So, ratio 8:3.
Downsream speed= d/4,
Upstream speed= 5d/44,
So, d/4 : 5d/44.
11: 5.
Now, the speed of the boat =(11+5)/2.
= 8.
The speed of the current =(11-5)/2.
= 3.
So, ratio 8:3.
(1)
Nitin Gusain said:
1 decade ago
Take it as in easy way
x= upstream speed
y= downstream speed
now we know that
upstream speed(x) = boat speed - stream speed
downstream speed(y) = boat speed + stream speed
so, x+y = 2*boat speed
x-y = 2*stream speed
so ratio of boat speed to stream speed is = (x+y)/(x-y)
x= upstream speed
y= downstream speed
now we know that
upstream speed(x) = boat speed - stream speed
downstream speed(y) = boat speed + stream speed
so, x+y = 2*boat speed
x-y = 2*stream speed
so ratio of boat speed to stream speed is = (x+y)/(x-y)
Amit lamba said:
1 decade ago
I got this trick
as y =speed of boat in downstream
so it ll be equal to = speed of boat + speed of water
x= speed of boat in upstream
so it ll = speed of boat - speed of water
so y +x/2 =(spd of boat)
simillerly y - x/2 =speed of water
So thats way they took this ratio.
as y =speed of boat in downstream
so it ll be equal to = speed of boat + speed of water
x= speed of boat in upstream
so it ll = speed of boat - speed of water
so y +x/2 =(spd of boat)
simillerly y - x/2 =speed of water
So thats way they took this ratio.
Balaji said:
9 years ago
Let u= man speed & v= stream speed.
We know downstream =u + v & upstream = u - v.
Then,
u - v = 8 + (48/60) = 8.8 hrs for upstream.
u = v = 4hrs for down stream.
Solving we get 6.4/- 2.4 (neglect sign).
Now, 6.4/2.4 = 64/24 = 8/3.
So, the answer is 8:3.
We know downstream =u + v & upstream = u - v.
Then,
u - v = 8 + (48/60) = 8.8 hrs for upstream.
u = v = 4hrs for down stream.
Solving we get 6.4/- 2.4 (neglect sign).
Now, 6.4/2.4 = 64/24 = 8/3.
So, the answer is 8:3.
Ashis said:
1 decade ago
As it is given to find out the ratio of speed of boat to speed of water w.r.to still water that is how required ratio is calculated.
You can find out from important formulae option i.e.
1/2(y-x)/1/2(y+x)
where y=speed at downstrem
x=speed at upstream.
You can find out from important formulae option i.e.
1/2(y-x)/1/2(y+x)
where y=speed at downstrem
x=speed at upstream.
Farru_faiz said:
6 years ago
If distance is equal thn formula
downstream X time 1 = upstream X time 2
downstream = U+V/2
upstream = U-V/2
downstream = speed of boat
upstream = speed of stream
i.e, U+V/2 * time 1 = U-V/2 * time 2
Now substitute the values in the above formula
downstream X time 1 = upstream X time 2
downstream = U+V/2
upstream = U-V/2
downstream = speed of boat
upstream = speed of stream
i.e, U+V/2 * time 1 = U-V/2 * time 2
Now substitute the values in the above formula
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