# 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:
107 comments Page 1 of 11.

How this required ratio? pls explain?
(1)

How can the y-x/2 become the current ratio?

Can you explain the process clearly?

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.

I didn't understand how 8*4/5 will get.

Given is 8 hr 48min so converting min to hr

We have 48/60=4/5

Thanks Ashis.

I am not able to understand the required ratio. ? how it is related with the speed of boat to speed of water. ?

I'm not able understand the ratio?can you give brief explanation.

Speed=distance/time
therefore distance=speed*time.
let consider speed at upstream is "x" and at downstream is "y", then distance covered (upstream in 8 hrs 48 min)= x*8*4/5

here 8hours and 48minutes=8*48/60=8*4/5

and distance covererd (downstream in 4hours=y*4

to relate both these equation
from question ,we know that distance covered are same

therefore x*8*4/5 = y*4

y=11/(5*x)
we know that speed are different in down stream and upstream.
if both are in same direction
take difference(x-y)
if they are in opposite
take sum(x+y)

required ratio =(x+y)/2 : (x-y)/2 // here 2 is to take average.