Volume sebuah balok 1.800 cm3, panjangnya = 15 cm, lebarnya= 6cm. Hitung luas permukaan balok.

1.800 = 15 x 6 x t
1800 = 90 t
t = 20cm

luas permukaan = 2pl + 2pt + 2lt
2 ( 15. 6 ) +  2 ( 15. 20 ) + 2 ( 6 . 20 )
2. 90 + 2. 300 + 2. 120
180 + 600 + 240
= 1020 cm²

p = 15 cm
l = 6 cm

Volume balok = 1800 cm³
p x l x t = 1800
15 x 6 x t = 1800
90 x t = 1800
t = 1800/90
t = 20 cm

L.perm.balok
= 2 (p x l) + 2 (p x t) + 2 (l x t)
= 2 (15 x 6) + 2 (15 x 20) + 2 (6 x 20)
= 2 (90) + 2 (300) + 2 (120)
= 180 + 600 + 240
= 780 + 240
= 1020 cm²