A family uses 2.5 quarts of milk per day. How many gallons of milk does the family use in 75 days
To convert quarts to gallons, divide the number of quarts by 4 because there are 4 quarts in a gallon.
2.5 quarts = 2.5/4 = 0.625 gallons
The family uses 0.625 gallons of milk per day, and in 75 days, they will use 0.625 x 75 = <<0.625*75=46.875>>46.875 gallons. Answer: \boxed{46.875}.