Jawabanmu

2014-09-10T19:25:22+07:00
Luas persegipanjang = PxL
Keliling persegipanjang = 2p+2l
Maka
56cm = P+1/3p+P+1/3p = 2 2/3P = 8/3 P
P = 56 : 8/3 = 21 cm
lebar persegi panjang = 1/3 p = 21:3 = 7cm
Maka luas persegipanjang = 21cmx7cm = 147cm²