Perbandingan rusuk balok adalah 2 : 3 : 5. Volume balok 1.920cm³. Berapa seluruh luas permukaan balok?

BALOK

misal
p : l : t = 2x : 3x : 5x

V = 1.920
p×l×t = 1.920
2x.3x.5x = 1.920
30x^3 = 1.920
x^3 = 1.920/30
x^3 = 64
x^3 = 4^3
x = 4 cm

p = 2x = 3×4 = 8 cm
l = 3x = 3×4 = 12 cm
t = 5x = 5×4 = 20 cm

Luas = 2×(pl + pt + lt)
Luas = 2×(8(12) + 8(20) + 12(20))
Luas = 2×(96 + 160 + 240)
Luas = 2×(496)
Luas = 992 cm^2

2x × 3x × 5x = 1920 cm³
30x³ = 1920 cm³
x³ = 1920 cm³/30
x³ = 64 cm
x = ∛64 cm
x = 4 cm

L = (2 × a × b) + (2 × b × c ) + (2 × a × c)
   = (2 × (2 × 4 cm) × (3 × 4 cm)) + (2 × (3 × 4 cm) × (5 × 4 cm)) + (2 × (2 × 4 cm) × (5 × 4 cm))
   = (2 × 8 cm × 12 cm) + (2 × 12 cm × 20 cm) + (2 × 8 cm × 20 cm)
   = 192 cm + 480 cm + 320 cm
   = 992 cm²