Jawabanmu

2014-05-20T08:13:48+07:00
Jumlah rusuk balok = 4p + 4l + 4t
160 = 4 × 4x + 4 × 3x +  4x
160 = 16 x + 12 x + 4x
160 = 32x
  x  = 160 : 32 = 5

p = 4 × 5 = 20 cm
l  = 4 × 5 = 15 cm
t  = 5 cm

Lp = 2(pl + pt + lt)
Lp = 2(20×15 + 20×5 + 15×5)
Lp = 2(300 + 100 + 75)
Lp = 2 × 475 = 950 cm²

V = plt
V = 20 × 15 × 5
V = 1500 cm³


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2014-05-20T08:29:50+07:00
P : l : t
4 : 3 : 1
4.4x : 3.4x : 1.4x
= 16x + 12x + 4x = 160
32x = 160
x =  \frac{160}{32} = 5

Panjang =  \frac{16(5)}{4} = 20cm
Lebar =  \frac{12(5)}{4} = 15cm
Tinggi =  \frac{4(5)}{4} = 5cm

a. Jumlah luas permukaan balok = 2 x ( p x l + p x t + l x t )
    = 2 x ( (20x15) + (20x5) + (15x5) )
    = 2 x ( 300 + 100 + 75 )
    = 950  cm^{2}

b. volume balok = p x l x t
    = 20 x 15 x 5
    = 1500  cm^{3}