Question 399818
It normally takes 2 h to fill a swimming pool.
 The pool has developed a slow leak.
 If the pool were full, it would take 10 h for all the water to leak out.
 If the pool is empty, how long will it take to fill it?
:
Let t = time to fill the pool, now that it is leaking
Let the completed job = 1; a full pool
:
{{{t/2}}} - {{{t/10}}} = 1
Multiply 10 to get rid of the denominators, results:
5t - t = 10
4t = 10
t = {{{10/4}}}
t = 2.5 hrs to fill the pool now