Question 439419
Both drainage pipes open at the same time, drain rate is
{{{1/180+1/120}}} pool per minutes.


Choose denominator 360.
{{{(2/2)(1/180)+(3/3)(1/120)}}}
{{{2/360+3/360}}}
{{{5/360}}}
{{{1/72}}}


Reciprocal of that will be minutes per pool

72 minutes to drain the pool.