The perimeter of the inside square is 1/√2 or (1 ÷ √2) the perimeter of the outside square, using the diameter (d).
OR
The perimeter of the inside square is (√2)/2 or (√2 ÷ 2) the perimeter of the outside square, using the radius (r).
1/√2 or (1 ÷ √2) = (√2)/2 or (√2 ÷ 2) = 0.707.
