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:
111 comments Page 1 of 12.
M Danish said:
4 weeks ago
Assume distance as 100 km.
Calculate Speed @ downstream (100/4hrs) = 25 km/h
Calculate speed @ upstream ( 100/ 8.8 hrs) = 11.36 km/h
Take the difference of both and divide by 2 to get the speed of the river.
(13.64/2)= 6.82 km/h.
To calculate the speed of the boat minus the speed of the river, from speed @ downstream (25-6.82) = 18.18 km/h.
Now as you have both speeds, calculate the ratio (18.18/6.82) = 2.66 = 8/3.
Calculate Speed @ downstream (100/4hrs) = 25 km/h
Calculate speed @ upstream ( 100/ 8.8 hrs) = 11.36 km/h
Take the difference of both and divide by 2 to get the speed of the river.
(13.64/2)= 6.82 km/h.
To calculate the speed of the boat minus the speed of the river, from speed @ downstream (25-6.82) = 18.18 km/h.
Now as you have both speeds, calculate the ratio (18.18/6.82) = 2.66 = 8/3.
(2)
Chandu said:
2 months ago
Upstream = boat - stream.
Downstream = boat + stream.
Distance is the same in both cases.
So,D(u.s) = D(d.s).
S×t = s × t.
(Boat+stream) × 8.8h = (boat - stream) × 4h.
Which gives the ratio.
Downstream = boat + stream.
Distance is the same in both cases.
So,D(u.s) = D(d.s).
S×t = s × t.
(Boat+stream) × 8.8h = (boat - stream) × 4h.
Which gives the ratio.
Anom said:
5 months ago
It was good. Thank you, @Anshul.
(1)
K srinivasarao said:
1 year ago
U. S = 8hrs * 60 + 48min = 528min
D. S = 4hrs * 60 = 240min.
Ratio = boat of speed=water speed
Boat speed= 528 + 240 = 768.
Water speed = 528 - 240 = 288.
Ratio = 768 : 288 = 8 : 3.
D. S = 4hrs * 60 = 240min.
Ratio = boat of speed=water speed
Boat speed= 528 + 240 = 768.
Water speed = 528 - 240 = 288.
Ratio = 768 : 288 = 8 : 3.
(85)
Amaya said:
1 year 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.
(8)
Sorsta said:
2 years ago
Well said, Thank you @Mahesh.
(4)
Likitha Ganta said:
2 years 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.
(29)
Hola amigos said:
2 years ago
I'm not getting this. Anyone, please help to understand the answer.
(17)
Sunil babu said:
2 years 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.
(9)
Mallika B said:
2 years 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.
(5)
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