Question 191310
the size of the tank is not a factor
so let's assume a size that's divisible by 30 and 45 ___ 90gal is good


the outlet passes 90gal in 30min or 3gal/min


the inlet passes 90gal in 45min or 2gal/min


with both open, the tank is losing 1gal/min (3-2)


emptying a 90gal tank at 1gal/min takes 90min