tolong yaa kak...............

D = 40 cm = R = 20 cm
t = 5,5 m = 550 cm
n = 15 buah
Lp = ...
Lp = n x 2 x π x R x t
    = 15 x 2 x 3,14 x 20 x 550
    = 1.036.200 cm