56.52:100.48
circumference is the diameter × π
diameter is radius × 2
first circle ->
r = 9
d = 9 × 2 = 18
c = 18 × π ≈ 56.52
second circle ->
r = 16
d = 16 × 2 = 32
c = 32 × π ≈ 100.48
so the ratio of circurfremce for 2 circles that have a ratio of radii 9:16 would be 56.52:100.48
