Question 301078
A large drain and a small drain are opened to drain a pool.
 The large drain can empty the pool in 6 hours.
 After both drains have been open 1 hour the large drain becomes clogged and is closed.
 The small drain remains open and requires 9 hours to empty the pool.
 How long would it have taken for the small drain working alone to empty the pool?
:
Let x = time for small drain alone
:
Let the completed job (a drained pool) = 1
:
Assume the small drain has been open for a total of 10 hrs
{{{1/6}}} + {{{10/x}}} = 1
multiply equation by 6x:
x + 10(6) = 6x
60 = 6x - x
5x = 60
x = {{{60/5}}}
x = 12 hrs, small drain alone