Perbandingan panjang, lebar, dan tinggi sebuah balok adalah 7: 5: 3. Jika volume balok 6. 720 cm tentukan panjang, lebar, tinggi balok dan luas permukaan

misal
p = 7x
l = 5x
t = 3x

V = p × l × t
6.720 = 7x • 5x • 3x
6.720 = 105x³
x³ = 6.720 ÷ 105
x³ = 64
x = ³√64
x = 4

jadi
p = 7x = 7 • 4 = 28
l = 5x = 5 • 4 = 20
t = 3x = 3 • 4 = 12

Lp = 2 × ( pl + pt + lt )
= 2 × ( 28•20 + 28•12 + 20•12 )
= 2 × ( 560 + 336 + 240 )
= 2 × 1136
= 2272 cm²