Question 921472
RATES
Pump Expected, {{{1/2}}}
Leak, {{{-1/u}}}
Pump Plus Leak,{{{1/(2&1/3)}}}


The rates are additive for the two agents working simultaneously.  The choice of giving the leak a negative sign or simply to subtract the absolute value depends on how you want to handle this; just understand that the pump and the leak are not in the same one-dimensional direction.


You can take u as a positive number;  your way of handling the sum of the rates could be either of these:
pump + leak = both together, and "leak" rate is a negative number.
OR
pump-leak=BothTogether, and "leak" rate is a positive number.


{{{highlight_green(1/2-1/u=1/(2&1/3))}}}


{{{1/2-1/u=1/(7/3)}}}
{{{1/2-1/u=3/7}}}
LCD is 14u
{{{7u-14=6u}}}
{{{highlight(u=14)}}}


The leak by itself can empty the tank in 14 hours.