Jawapan

2015-03-05T15:58:19+08:00
Jumlah panjang sisi = 4(p+l+t)
4 (x+x+y) = 64
     2x + y = 64/4
     2x + y = 16
             y = 16 - 2x

jumlah luas permukaan = 2{(p×l)+(p×t)+(l×t)}
2 {(x.x) + (x.y) + (x.y)} = 160
             2 {x² + 2xy} = 160
                   x² + 2xy = 160/2
                   x² + 2xy = 80

subtitusikan
x² + 2x (16-2x) = 80
x² + 32x - 4x² = 80
x² - 4x² + 32x - 80 = 0
-3x² + 32x - 80 = 0
3x² - 32x + 80 = 0
x₁ = 20/3
x₂ = -4  ( negatif tidak memungkinkan)

isipadu= \frac{20}{3} \times \frac{20}{3}(16-2. \frac{20}{3}) \\ ~~~~~~~~~~~= \frac{20}{3}\times \frac{20}{3}(16- \frac{40}{3} ) \\ ~~~~~~~~~~~= \frac{20}{3}\times \frac{20}{3}\times( \frac{48}{3} -\frac{40}{3} ) \\  ~~~~~~~~~~~= \frac{20}{3}\times \frac{20}{3}\times \frac{8}{3}  \\  ~~~~~~~~~~~= \frac{3200}{27} \\  ~~~~~~~~~~~= 118,51