Question

increase in area ∆A=12.7%,∆A=360mm,d=?

Answer 1

ΔA = 12.7% of A = 0.127 A
ΔA = 360 mm
A = 360/0.127 = 2834.6 (rounded off)
$a = \pi {r}^{2}$
r = 30.0 mm
d = 2r = 60.0 mm