Adding up the lengths of the exposed sides of the square would give you 40. You do not count the sides of the square in the middle because it's being covered by the 2 half circles.
We can use the 2 squares to measure the half circles. Since the circles cover 2 sides of the square, the circle is 20 units long on the flat side. To find the perimeter of the curves, you would at Pi into the equation.
