please bantu jawab No 13

Luas juring = 108°/360° × 3,14 × r^2
211,95 = 0,3 × 3,14 × r^2
211,95 = 0,942 r^2
211,95 ÷ 0,942 = r^2
225 = r^2
r = √225 = 15cm
^ artinya pangkat