<PRE><B>Question 291776</B>
A sink can be filled in 3 minutes. Suzi is filling and draining the sink at the same time. 
In 15 minutes the sink starts to overflow.
 How many minutes does it take to drain the sink?
:
Let x = time required to drain the sink
:
Let the full sink = 1
:
Filling (+)  draining(-) 
{{{15/3}}} - {{{15/x}}} = 1
multiply equation by 3x
15x - 3(15) = 3x
15x - 45 = 3x
15x - 3x = 45
12x = 45
x = {{{45/12}}}
x = 3.75 minutes to drain a full sink
;
:
Check solution
{{{15/3}}} - {{{15/3.75}}} =
5 - 4 = 1
</PRE>