Mary is building a mosaic for her school cafeteria's wall. It will be 10 feet tall and 15 feet long. Each tile she uses is 1 inch square. How many tiles will she need? Think carefully first, then make a decision:
First convert the length of the mural to inches: 15 feet * 12 inches / foot = 180 inches. Then convert the height of the mural to inches: 10 feet * 12 inches / foot = 120 inches. Then multiply the length and the height to find the total area of the mural: 180 inches * 120 inches = 21600 square inches. Since each tile is 1 square inch, this is also the number of tiles she needs. So, the answer is 21600.