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:
107 comments Page 1 of 11.
Amaya said:
1 month ago
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.
i.e.
d=d
44/5 x = 4y
by further solving
11x - 5y =0 i.e. y=11/5x ---> eq(1)
They have x = speed of the boat - speed of the current = u-v.
And y = speed of boat + speed of the current = u + v.
From eq(1).
u-v = 11/5(u + v).
u/v = 8/3.
i.e. u:v = 8:3.
Then, distance covered upstream in 8 hrs 48 min = Distance covered downstream in 4 hrs.
i.e.
d=d
44/5 x = 4y
by further solving
11x - 5y =0 i.e. y=11/5x ---> eq(1)
They have x = speed of the boat - speed of the current = u-v.
And y = speed of boat + speed of the current = u + v.
From eq(1).
u-v = 11/5(u + v).
u/v = 8/3.
i.e. u:v = 8:3.
(1)
Sorsta said:
5 months ago
Well said, Thank you @Mahesh.
(1)
Likitha Ganta said:
9 months ago
(x-y)8*48/60 = (x+y)4,
(x-y)8*4/5 = (x+y)4,
(44/5)x-(44/5)y = 4x+4y,
(44/5)x-4x = 4y+(44/5)y,
(44x-20x)/5 = (20y+44y)/5,
24x = 64y,
= 3 : 8.
(x-y)8*4/5 = (x+y)4,
(44/5)x-(44/5)y = 4x+4y,
(44/5)x-4x = 4y+(44/5)y,
(44x-20x)/5 = (20y+44y)/5,
24x = 64y,
= 3 : 8.
(18)
Hola amigos said:
11 months ago
I'm not getting this. Anyone, please help to understand the answer.
(10)
Sunil babu said:
11 months ago
@Mallika B.
They have x = speed of the boat - speed of the current.
And y = speed of boat + speed of the current.
So y - × = 2 * (speed of boat),
Then (y-x)/2 = speed of the boat.
They have x = speed of the boat - speed of the current.
And y = speed of boat + speed of the current.
So y - × = 2 * (speed of boat),
Then (y-x)/2 = speed of the boat.
(6)
Mallika B said:
1 year ago
Can somebody please explain why have we done (y-x/2) in the required ratio step? If that is associated with downstream, why are we subtracting?
Please explain me.
Please explain me.
(3)
Lakaka said:
1 year ago
Thank you. @Tushar Pawar.
(4)
Amar The macho man said:
2 years ago
Given,
Time (upstream)=8 hour 48 min=(8*60+48) = 528 min.
Time (downstream)= 4 hour = (4*60)min = 240 min.
Let distance be x.
we know speed =distance/time.
so, the speed of the boat (upstream) = distance/time.
= x/528.
speed of the boat (downstream) = distance/time.
= x/240.
We know that;
speed of boat in still water = (downstream+upstream)/2.
= (x/240 + x/528)/2.
= x/330.
We know that
speed of stream/current water.
= (downstream-upstream)/2.
So we have to find the ratio of the speed of the boat in still water by the speed of the stream/current =
(x/330)/(x/528)=8/3 or 8:3
Therefore, ratio = 8:3 Answer.
Time (upstream)=8 hour 48 min=(8*60+48) = 528 min.
Time (downstream)= 4 hour = (4*60)min = 240 min.
Let distance be x.
we know speed =distance/time.
so, the speed of the boat (upstream) = distance/time.
= x/528.
speed of the boat (downstream) = distance/time.
= x/240.
We know that;
speed of boat in still water = (downstream+upstream)/2.
= (x/240 + x/528)/2.
= x/330.
We know that
speed of stream/current water.
= (downstream-upstream)/2.
So we have to find the ratio of the speed of the boat in still water by the speed of the stream/current =
(x/330)/(x/528)=8/3 or 8:3
Therefore, ratio = 8:3 Answer.
(51)
Tushar Pawar said:
2 years ago
Distance Upstream = Distance Downstream.
Speed Upstream * Time Upstream = Speed Downstream * Time Downstream.
(x - y) * 44/5 = (x + y) * 4,
24x = 64y,
x:y = 8:3.
Speed Upstream * Time Upstream = Speed Downstream * Time Downstream.
(x - y) * 44/5 = (x + y) * 4,
24x = 64y,
x:y = 8:3.
(112)
Sourav ghosh said:
2 years ago
Thanks for this short trick @Mahesh.
(6)
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