Perbandinga panjang dan lebar persegi panjang 8:5 jika keliling 78 maka luas

jawab
perbandingan
p:  l= 8: 5
misalkan 
p= 8a
l = 5a
K= 78  --> 2 (p+l) = 78
p + l = 39
8a + 5a = 39
13 a = 39
a = 3

p = 8a = 8(3) = 24
l = 5a = 5(3) = 15