"Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."
- Albert Einstein
4.
A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is:
Hai, Mr. Rajesh Kumar, can you explain me in brief?
John said:
(Fri, Jul 8, 2011 10:07:01 AM)
How it is possible to multiply the speed of upstream and downstream?
Bhavani said:
(Mon, Jul 18, 2011 12:22:05 PM)
Explain briefly.
Jyoti said:
(Sun, Jul 31, 2011 08:09:47 AM)
Hello friends,
In this Speed of the boat in still water is given that is 15Km/s. and here we find speed of stream. take the answer from bottom suppose i take 10 from bottom.
You can see that speed of boat in upstream become15-10=5 and distance of upstream is 30 given. Here you can find out the time in case of upstream time=dist/speed 30/5=6.
Similarly speed in case of downstream 15+10=25. Distance 30 given time you can find that is=30/25=6/5. In question, we have given total time 4hr 30min. We can see that the answer 10 is choosen by me is wrong. Take 5 in place of 10 you get the answer.
Folake said:
(Thu, Sep 8, 2011 05:57:33 PM)
I don't really understand this question. Some one should please help me out.
Vinoth said:
(Wed, Sep 28, 2011 02:30:20 PM)
Simply follow formula when only distance the, time t and speed of boat x given.. and asked for speed of stream.... use in formula,
d^2/(x^2-y^2)=t ,
9/2=(225-y^2)/15, ==> y^2=25 , y=5
Seetha said:
(Fri, Oct 7, 2011 03:24:14 PM)
Here we have been given the speed of the boat is 15 kmph that too in still water and the boat goes and comes back in 4 and half hour and that distance is 30 kms so we have to find the speed of the stream in kmph.
Let us think that the speed of the stream be X then
We know that Speed of the downstream is (u+v) here u is speed of the boat and v is speed of the stream so
Speed of downstream is (15+x)Kmph
Speed of upstream is (15-x)Kmph
We know that
speed in still water is 1/2(a+b) kmph
so
30/(15+x) + 30/(15-x) = 4 1/2
Rohit Chavan said:
(Mon, Nov 21, 2011 10:23:49 PM)
Total time=(distance of downstream/speed of downstream)+(distance of downstream/speed of downstream)
Therefore, (30/(15+x))+(30/(15-x)) = 9/2 hrs
Then find the value of x by simplifying the above equation.
Sunil Sharma, Kaverinagar said:
(Wed, Mar 21, 2012 12:30:16 AM)
How can you multiply in place of addition ?
Varun said:
(Sat, May 19, 2012 08:01:41 PM)
Here only one direction distance is given. Time which requires to go and back position is given. How is possible to put total time to only one direction distance.
Jagu said:
(Fri, Jun 15, 2012 05:24:27 PM)
How we get 9/2 there please tell me.
Neha said:
(Sat, Aug 18, 2012 05:36:54 PM)
By solving the fraction 4*2=8, n 8+1=9, so the ans is 9/2
