Jawabanmu

2014-09-10T19:25:43+07:00
Kll = 56
lebar = 10 m
panjang = 56 - ( 10 + 10 ) = 56 - 20 = 36 : 2 = 18 m
jadi panjangnya = 18 m

luas = P x L 
        =  10 x 18 = 180 m²
om kolo panjang = 18, lebarnya jadi panjang - 8 = 10
sementara di soal lebar = panjang - 10
2014-09-10T19:26:47+07:00
P = panjang, l = lebar, L= luas

k = p + p + p-10 + p-10 = 56 m
k = 4p -20 = 56 m
4p = 76
panjang = 76/4 = 19 m
lebar = 19 - 10 =  9 m
keliling = 19+19+9+9 = 56 m  
Luas    = p×l =19 ×9 = 171 m