No 13 Pakai cara ya.. Trimakasihh

t = 2r
d = 2r
r = r

L. Permukaan Tabung = 2π r t (r + t)
= 2 x π x r (r + 2r) 
= 2 x π x (r² + 2r²)
= 2π x 3r²
= 6πr²

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