<PRE><B>Question 258175</B>
A full tank can be emptied in 30 minutes if the drain
is opened and an empty tank can be filled in 45 minutes
with the inlet pipe opened. If both pipes are accidentally
opened when the tank is full, then how long will it take to
empty the tank?
-------------------------------------------------
Filling tank DATA:
rate = 1/30 job/min
------
Emptying tank DATA:
rate = 1/45 job/min
---------------------
Together DATA:
rate = 1/x job/min
==========================
Equation:
rate - rate = together rate
1/30 - 1/45 = 1/x
---
(45-30)/(30*45) = 1/x
15x = 30*45
x = 90 minutes (amt. of time needed to fill the tank)
==================
Cheers,
Stan H.
</PRE>