* Know the conversion: 1 quart = 1/4 gallon

* Calculate half gallons:

* 2.25 quarts * (1/4 gallon/quart) = 0.5625 gallons

* Convert to half gallons: 0.5625 gallons * (2 half gallons/gallon) = 1.125 half gallons

Therefore, 2.25 quarts is equal to 1.125 half gallons.