Question 189865
This is a problem adding rates to get a combined rate
You can say that drainage is expressed in pools/minute
For instance, 1 pool/30 sec would be 2 pools/min drained
For this problem in words:
(1st pipe drainage rate) + (2nd pipe drainage rate) = 
(both pipes together drainage rate)
Let {{{t}}} = the time to drain the pool with both pipes open
Given:
{{{1/150 + 1/225 = 1/t}}}
Multiply both sides by {{{450}}}
{{{3 + 2 = 450/t}}}
Multiply both sides by {{{t}}}
{{{5t = 450}}}
{{{t = 90}}}
With both pipes are draining together, it takes 90 min to empty the pool
How many liters of water are in the pool
doesn't matter in this problem