diketahui luas selimut tabung 528 cm² tinggi 12 cm dan phi 22/7 ,maka panjang diameter alas tabung itu adalah

luas selimut = 528 cm²
p x l = 528 cm²
12 cm x l = 528 cm²
lebar = 528 cm² : 12 cm
lebar = 44 cm

lebar selimut = keliling alas
keliling alas = 44 cm
22/7 x diameter = 44 cm
diameter = 44 cm : 22/7
diameter = 44 cm x 7/22
diameter = 2 cm x 7
diameter = 14 cm

Lst = 2 x π x r x t
528 = 2 x 22/7 x r x 12
528 = 2 x 22 x 12 x r
               7
528 = 528 x r
           7
528 x 7 = r
  528
3696 = r
 528
7 = r
r = 7 cm