To be able to get the enlarged dimensions, we will multiply the dimension of the poster by the given scale factor 5/2.
We get,
[tex]\text{Width = 3 ft. x }\frac{5}{2}\text{ = }\frac{15}{2}\text{ ft. or 7.5 ft.}[/tex][tex]\text{Length = 12 ft. x }\frac{5}{2}\text{ = }\frac{60}{2}\text{ ft. or 30 ft.}[/tex]Therefore, the enlarged dimension of the poster will be 7.5 ft. x 30 ft.
