To find the total area covered by the pictures, I need to multiply the area of one picture by the number of pictures. The area of one picture is 9 times 12, or 108 square inches. So the total area covered by the pictures is 108 times 11, or 1188 square inches. 
Eleven rectangular 9-inch by 12-inch pictures hang on a wall. How many square inches of the wall's surface area are covered by the pictures?