tolong kerjakn beserta jalan nya. soal nya aku kurang ngertii☹

no 1 luas selimut = 2 x pi x r x t
cari t = 2 x 3.14 x 12.5 x 12.5 + 2 x 3.14 x 12.5 x t = 2315.75 dm 2
78.5 t = 2315.75 - 981.25 = 1334.5
t = 1334.5 ÷ 78.5 = 17 dm
luas selimut tabung = 2 x 3.14 x 12.5 x 17
= 1334.5 dm2
no 2 luas permukaan= 2 x pi x 3.5 x 3.5 + 2 x pi x 3.5 x t
t = luas selimut 2 x pi x 3.5 x t = 4400
t = 200
luas permukaan = 11 x 0.5 x 3.5 + 11 x 0.5 x 200 = 19.25 + 1100 = 1119.25 cm2