A fish tank in a pet store was less than half full of
water when a worker turned on a hose to fill the
tank at a constant rate. After the hose was on for
5 minutes, the tank was exactly half full. After
the hose was on for 30 minutes, the tank was
three-quarters full. How many minutes did it take
after the hose was turned on for the tank to be
completely filled with water?