To find the ratio of their perimeters, you need to know that the ratio of a perimeter is the square root of the ratio of the areas. (Area is 2 dimensional, so what you do to the perimeter will have twice or be squared for the area).
So, you would simplify the ratio of 18/32 to 9/16.
Then take the square root of 9 and 16 separately to find the ratio of the perimeters.
Square root of 9 is 3.
Square root of 16 is 4
So, the ratio of the perimeters is 3 in/4 in.
