perbandingan panjang dan lebar persegi panjang 8:5 jika kelilingnya 78 m maka luasnya adalah... tolong sama carannya

Panjang : lebar = 8 : 5
p : l = 8 : 5
p = 8/5 l
Keliling = 78 m
Maka
K = 2 (p + l)
78 = 2 (8/5 l + l)
78 = 2 (8/5 l + 5/5 l)
78 = 2 (13/5 l)
78 × 5 = 2 × 13 l
390 = 26 l
l = 390/26
l = 15 m

p = 8/5 l = 8/5 (15) = 8 × 3 = 24m

L = p × l = 15 × 24 = 360 m²

2 (p+l) = 78
p + l = 39
p : l = 8 : 5
p = 8 : (8+5) × 39
p = 8 : 13 × 39
p = 24 meter

l = 5 : (8+5) × 39
l = 5 : 13 × 39
l = 15 meter

Luas = p × l
= 24 × 15 = 360 meter persegi