"If you judge people, you have no time to love them."
- Mother Teresa
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?
[A].
2 : 1
[B].
3 : 2
[C].
8 : 3
[D].
Cannot be determined
[E].
None of these
Answer: Option C
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.
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.
Ravi said:
(Wed, Feb 23, 2011 12:44:46 PM)
I didn't understand how 8*4/5 will get.
Bharath said:
(Fri, Feb 25, 2011 12:44:09 PM)
Given is 8 hr 48min so converting min to hr
We have 48/60=4/5
Phani said:
(Thu, May 26, 2011 01:19:21 AM)
Thanks Ashis.
Anchal said:
(Mon, Jun 6, 2011 02:58:08 AM)
I am not able to understand the required ratio. ? how it is related with the speed of boat to speed of water. ?
Gita said:
(Thu, Jun 16, 2011 03:45:38 PM)
I'm not able understand the ratio?can you give brief explanation.
Binza said:
(Sat, Jul 9, 2011 01:18:32 PM)
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.
then answer is 8:3
Navya said:
(Wed, Jul 20, 2011 03:08:03 AM)
I got it. 8*5+4=44.
Fractions!
Raja said:
(Wed, Jul 27, 2011 02:39:53 PM)
8hr48min we need to convert 8hr48min in terms of only hr because we are required to compare 8hr48min to 4hr....and in 4hr there are no unit of any min therefore we have to convert 8hr48min in only hr ok....and 8 is already given in hr....
so that we will convert only 48min in terms of hr
60min=1hr
1min=1/60
similarly...
60min=1hr
1min=1/60
48min=(1/60)*48=48/60hr
[8(48/60)]hr=8(4/5)=8*5+4=40+4=44
Prasanth said:
(Wed, Aug 31, 2011 07:30:42 PM)
@Binza
your explantation is not correct. This is not train problem to take like that. Speed of boat supported by extra speed of water current when down stream and reduced in up stream.
Pankaj said:
(Wed, Sep 7, 2011 12:21:38 AM)
@ prasanth
binza concept is correct,but i still does't understand the avg?????
Bindu said:
(Sun, Sep 11, 2011 07:42:26 AM)
As distance is same formula will be upstream speed X time1 =downstream speed x time 2
as y =speed of boat in downstream
so it ll be equal to = speed of boat + speed of water
x= speed of boat in upstream
so it ll = speed of boat - speed of water
so y +x/2 =(spd of boat)
simillerly y - x/2 =speed of water
So thats way they took this ratio.
Sangu said:
(Sat, Oct 8, 2011 10:41:39 PM)
Its the ratio between speed of the upstream and speed of the down stream.
Formula is (a+b)/2:(a-b)/2.
See the formula you will get it.
Rakesh said:
(Fri, Nov 11, 2011 07:18:09 PM)
@sangu
Thank u a lot..
Gautam said:
(Wed, Dec 28, 2011 09:45:47 PM)
Let the man's rate upstream be U kmph and that downstream be V kmph.
Then, distance covered upstream in 8 hrs 48 min = Distance covered downstream in 4 hrs.
Required ratio =