volume sebuah balok tanpa tutup 8.640 cm . jika perbandingan p::;t=5:3:9, luas permukaan balok tersebut...cm

V = p × l × t
8640 = 5x × 3x × 9x
8640 = 135x³
64 = x³
³√64 = x
4 = x

p = 5x = 5 × 4 = 20 cm
l = 3x = 3 × 4 = 12 cm
t = 9x = 9 × 4 = 36 cm

luas permukaan = 2(pl + pt + lt)
= 2(20 × 12 + 20 × 36 + 12 × 36)
= 2(240 + 720 + 432)
= 2(1392)
= 2784 cm²