Diketahui balok 385 cm3 panjang lebar tinggi balok berturut 11 cm 5cm dah(3+x) luas permukaan balok tersebut

V = p × l × t
385 = 11 × 5 × (3 + x)
385 = 165 + 55x
220 = 55x
x = 4

t = 3 + 4 = 7

Lp = 2(pl + pt + lt)
= 2(55 + 77 + 35)
= 2(167)
= 334 cm2

Dik:
p = 11
l = 5
t = (3 + x)
V = 385

Dit:
Lp = ............. ?

Jwb:
V = p . l . t
385 = 11 . 5 . (3 + x)
385 = 55 . (3 + x)
385/55 = 3 + x
7 = 3 + x
7 - 3 = x
x = 4

t = 3 + x
t = 3 + 4
t = 7

Jadi,
Lp = 2(pl + pt + lt)
Lp = 2(11.5 + 11.7 + 5.7)
Lp = 2(55 + 77 + 35)
Lp = 2(167)
Lp = 334 cm²