why does total perimeter/required perimeter doesn’t work?

Perimeter of Square is 36 i.e. each side will be of length 9 (9x4 = 36) and area covered by it is S^2 =9^2 \text{ OR } 81, Now, we have been given length and width of the rectangle thus, total area of this rectangle is 36x72 = 2592.

If you rephrase the question it is asked how many square are required to fit the area of the rectangle

or \dfrac{2592}{81}=32

Another method is that you can look at width and height individually and then product them.

Width of rectangle = 36 and length of square = 9, thus, we need \dfrac{36}{9}= 4 squares

Height of rectangle = 72 and length of square = 9, thus, we need \dfrac{72}{9}= 8 squares

Hence, In total we need 4 x 8 = 32 squares

Also, the perimeter is a trap word in a sense that it can trick you into calculating the perimeter of rectangle