Jawabanmu

2014-06-10T14:47:58+07:00
Panjang x Lebar = Luas Persegi Panjang
3x x 4x = 108cm²
12x² = 108cm²
x² = 108 : 12
x² = 9
x = √9
x = 3

Panjang = 3x3 = 9
Lebar = 3x4 = 12

Keliling = Panjang + Panjang + Lebar + Lebar
           = 9cm + 9cm + 12cm + 12cm
           = 42cm.

Semoga Membantu
2014-06-10T15:15:59+07:00
L = p × l
108 = 3α × 4α
108 = 12α²
a² = 108 ÷ 12
   = 9
α = √9
 α  = 3
  
p : l
3.3 : 4.3
9 : 12
 K = 2 (p+l)
   = 2 (9+12)
  = 2 ( 21 )
 = 42 cm ..