Two similar posters of transformers were displayed in a shop. The area of the larger posters is 117 cm square and the area of the smaller is 52 cm square. If the width of the larger is 18 cm, find width of the smaller.
The areas of two similar figures area proportional to the square of their corresponding sides, so
w^2/18^2 = 52/117
w^2 = 144
w = √144 = 12