A pipe connected with a tank or a cistern or a reservoir, that fills it, is known as an
inlet.
Outlet:
A pipe connected with a tank or a cistern or a reservoir, emptying it, is
known as an outlet.

2. (i)

If a pipe can fill a tank in x hours, then :-
part filled in 1 hour = 1/x

(ii)

If a pipe can empty a full tank in y hours, then :-
part emptied in 1 hour = 1/y

(iii)

If a pipe can .fill a tank in x hours and another pipe
can empty the full tank in y hours
(where y> x), then on opening both the pipes,
the net part filled in 1 hour = (1/x)-(1/y)

(iv)

If a pipe can fill a tank in x hours and another pipe
can empty the full tank in y hours (where
x > y),
then on opening both the pipes,
the net part emptied in 1 hour = (1/y)-(1/x)