tolong di bantu dengan cara yang jekas ya

r :t = 3 : 5 ==> r/t = 3/5 => t = 5/3 r

LuasSelimut = 480phi
2×phi×r×t = 480phi
r×t = 480phi/2phi
r×t = 240
r × (5/3 r) = 240
r^2 = 240 × 3/5
r^2 = 48 × 3
r^2 = 144
r^2 = 12^2
r = 12 cm

Jwb. D