ΔABC is an equilateral with each side length equal to diameter. ABHI, ADEC and BCFG are rectangles. Also, ∠IAD = ∠FCE = ∠IAD = 360 – ∠IAB – ∠CAD – ∠BAC = 360 – 90 – 90 – 60 = 120 = ∠HBG = ∠FCE. Now, length of the rubber band is, HI+ID+DE+EF+FG+GH =3d+3×