Question

Perbandingan ukuran panjang,lebar,tinggi adalah5:4:2.jika volume baloj tersebut adalah 1.080cm3 maka luas alasnya adalah

Answer 1

Rasio p : l : t = 5 : 4 : 2
V = 1.080 cm³
misal 
p = 5x
l = 4x
t = 2x
5x × 4x × 2x = 1.080
40x³ = 1.080
x³ = 1.080 ÷ 40
x³ = 27
x = 3 cm
jadi, 
p = 5 ×3 = 15
l = 4× 3 = 12
t = 2 × 3 = 6
L.permukaan balok = 2( pl + pt + lt )
L.permukaan balok = 2( 15×12 + 15×6 + 12×6)
L.p Balok = 2 ×342
L.p Balok = 684 cm²

Answer 2

P = 5x ⇒ 5x = 5(3) = 15
l = 4x  ⇒ 4x = 4(3) = 12
t = 2x  ⇒ 2x = 2(3) = 6

V = p x l x t
1.080 = 5x x 4x x 2x
1.080 = 40x³
1.080/40 = x³
          x³ = 27
           x = ∛27
           x = 3

Lp = 2(pl + pt + lt)
     = 2(15×12 + 15×6 + 12×6)
     = 2( 180 + 90 + 72 )
     = 2(342)
     = 648 cm²