<PRE><B>Question 392226</B>
Mr kumar lives in the eastern part of singapore. He visits his aged parents, who lives 36 km away, every weekend.He finds that if he increases the average speed of his vehicle by 12 km/h, he could save 9 minutes of his travelling time.Find the speed at which he travels before the increase in speed.

--------
Original DATA:
distance = 36 km ; rate = x km/h ; time = d/r = 36/x hrs
=========================
New DATA:
distance = 36 km ; rate = x+12 km/h ; time = 36/(x+12) hrs
-------------
Equation:
Old time - New time = 9/60 hrs.
---------------
36/x - 36/(x+12) = 9/60
---
4/x - 4/(x+12) = 1/60
--------
60*4(x+12) - 60*4x = x(x+12)
60*4*12 = x^2+12x
----
x^2+12x-2880 = 0
x =  48 km/h (original rate)
===========
Cheers,
Stan H.
===========</PRE>