# 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?
2 : 1
3 : 2
8 : 3
Cannot be determined
None of these
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

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.
(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?

(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
(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.
(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!
(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
(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.
(7)