Jawabanmu

2014-03-14T12:42:10+07:00
K = 2(p+l)
81 = 2 (5x+4x)
81 = 2(9x)
81 = 18 x
x = 81 /18
x = 4,5 m

panjang = 5x = 5.4,5 = 22,5 m
lebar = 4x = 4.4,5 = 18 m

Luas ladang = p x l
                   = 22,5 m x 18 m
                   = 405 m²
2014-03-14T14:25:36+07:00
Perbandingan= 5:4
5+4=9
5/9×81=45cm
4/9×81=36cm

45/2=22.5 cm
36/2=18 cm
L Persegi panjang = p×l
22.5×18=405 cm2