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:
104 comments Page 1 of 11.
Hola amigos said:
2 months ago
I'm not getting this. Anyone, please help to understand the answer.
Sunil babu said:
2 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.
(2)
Mallika B said:
3 months 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.
(2)
Lakaka said:
5 months ago
Thank you. @Tushar Pawar.
(3)
Amar The macho man said:
10 months 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.
(23)
Tushar Pawar said:
1 year 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.
(71)
Sourav ghosh said:
1 year ago
Thanks for this short trick @Mahesh.
(3)
Aman sankhyan said:
2 years ago
@All.
You did not mention which speed of the boat to be calculated if it was in the still water or downstream or against the stream!
You did not mention which speed of the boat to be calculated if it was in the still water or downstream or against the stream!
(2)
Mahesh said:
2 years ago
When the same distance is mentioned in this type of question best shortcut is the sum:difference. Nothing but 12hr 48 min: 4hr 48min.
Other than change completely minutes. so 768min:288 min = 8:3
Other than change completely minutes. so 768min:288 min = 8:3
(38)
Anshul said:
2 years ago
Speed = Distance/Time.
Downstream = (u-v) km/hr.
Upstream = (u+v) km/hr.
Converting time to mins gives;
8hrs. 48 mins = 528 mins.
4 hrs. = 240 mins.
Let, Distance travelled = x km.
Therefore,
u-v = x/528 ----> 1.
u+v = x/240 ----> 2.
On dividing 1/2.
Therefore, (u-v)/(u+v) = 240/528 = 10/22.
On solving u/v = 32/12 = 8/3.
Downstream = (u-v) km/hr.
Upstream = (u+v) km/hr.
Converting time to mins gives;
8hrs. 48 mins = 528 mins.
4 hrs. = 240 mins.
Let, Distance travelled = x km.
Therefore,
u-v = x/528 ----> 1.
u+v = x/240 ----> 2.
On dividing 1/2.
Therefore, (u-v)/(u+v) = 240/528 = 10/22.
On solving u/v = 32/12 = 8/3.
(7)
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