The perimeter of the rectangle is 48 cm.
Step-by-step explanation:
Let the width of the rectangle = x
The length of the rectangle = 2x
so area =L X B = x X 2x = 
The each side of the square is 12 cm
so area = 12 X 12 sq cm = 144 sq cm
According to the problem,
= 144
or,
= 144/2 = 72
or, x = 
= 8.4 = 8 (approx)
so length = 16 cm and width = 8 cm
Perimeter = 2 X ( L + B) = 2 X (16+8) = 48 cm