Jika diketahui perbandingan panjang dan lebar persegi panjang adalah 6:4 dan keliling 80 cm maka tentukan : a.ukuran panjang dan lebarnya b. luas persegi panjan

panjang = 6x
lebar = 4x

keliling = 2p + 2l
80 = 2(6x) + 2(4x)
80 = 12x + 8x
80 = 20x
x = 80/20 = 4

a)

panjang = 6x = 6.4 = 24 cm
lebar = 4x = 4.4 = 16 cm

b)

L = p.l = 24.16 =  384 cm2

p : l = 6 : 4
Misal :
p = 6x
l = 4x

Keliling = 80 cm
2p + 2l = 80
2 (6x) + 2 (4x) = 80
12x + 8x = 80
20x = 80
x = 80/20
x = 4 cm

p = 6x = 6 (4) = 24 cm
l = 4x = 4 (4) = 16 cm

Luas persegi panjang
= p x l
= 24 x 16
= 384 cm²