"I never think of the future. It comes soon enough."
- Albert Einstein
8.
A boat takes 90 minutes less to travel 36 miles downstream than to travel the same distance upstream. If the speed of the boat in still water is 10 mph, the speed of the stream is:
I dont understand from where the 60 comes. is it a concept or derived from theose data? pls explain.
You should multiply (10 - x) and (10 + x) as to take LCM, so that you can substract the numeraters i.e. 36-36.
You knew that (a+b) x (a-b) = (a2 - b2) , (NOTE: read it as a square minus b square.)
And in order to multiply the denominators you got to multiply them with the numerators also; so, you get 36(10+x) - 36 (10-x), this is divided by (100 - x2 -i.e.square)
But what i do not understand is from where does that 60 come?
Anyone?
Bhimu said:
(Fri, Apr 22, 2011 01:58:36 PM)
60 is to convert min to hour.
Karthik said:
(Sat, May 14, 2011 09:58:00 AM)
Why we should convert min to hour anybody?
Abc said:
(Tue, May 17, 2011 11:17:44 AM)
Because the unit is in hours.
Noah said:
(Tue, May 17, 2011 11:19:33 AM)
Can any body explain this?
A boat takes 90 minutes "less" to travel. Then why do we write the equation = 90?
Suji said:
(Wed, Jun 1, 2011 01:53:11 AM)
we can also take like that....
it is easy to form eqn like above
ie difference between upstream and downsttream
..
Keerthan said:
(Thu, Jun 30, 2011 07:26:38 AM)
I didn't get from wer did the 60/90 ratio come! can anybody?
Rohit Chavan said:
(Mon, Nov 21, 2011 10:55:25 PM)
Downstream speed = (upstream speed-90); _____(because downstream takes 90 min less then upstream.)
Hence, (90/60)min=(36/(10-x))+(36/(10+x));
and proceed as given in solution i.e. simplify the equation.
Rohit Chavan said:
(Mon, Nov 21, 2011 11:07:06 PM)
Given Condition:(upstream speed-(90/60)min)=downstream speed;
72x x 60 = 90 (100 - x2)