Final answer:
To cover a ceiling measuring 12 feet by 18 feet, 18 packages of ceiling tiles measuring 1 foot by 2 feet (6 per package) are required. Divide the ceiling area (216 square feet) by the coverage area of one package (12 square feet) to determine the quantity needed.
Step-by-step explanation:
To determine how many packages of ceiling tiles are needed for a rectangular ceiling that measures 12 feet by 18 feet, first calculate the total area of the ceiling. Since each tile measures 1 foot by 2 feet, each tile covers an area of 2 square feet. The area of the 12x18 feet ceiling is 12 * 18 = 216 square feet.
Now, divide the area of the ceiling by the area covered by one package of tiles. Since each package contains 6 tiles, and each tile covers 2 square feet, one package covers 6 * 2 = 12 square feet. Thus, 216 square feet / 12 square feet per package = 18 packages. Therefore, you would need 18 packages to cover the ceiling.
Make sure to buy an extra package to account for any mistakes or damages during the installation process.