Answer:
84.85cm
Step-by-step explanation:
Let the sides of the square be x
The perimeter of the square = 4x
Get x using the pythagoras theorem
x^2 + x^2 = 30^2
2x^2 = 900
x^2 = 450
x = 21.21cm
Perimeter of the plate = 4(21.21)
Perimeter of the plate = 84.85cm
c
√x^72 = √(x^36)^2 = x^36