Keliling taman berbentuk persegi panjang 42cm jika panjang :lebar =4:3,maka luasnya.... Cm² A.84 B. 108 C. 216 D. 440

PERSEGI PANJANG

K = 42
2×(p+l) = 42
p+l = 42/2
p+l = 21

p:l = 4:3

gunakan konsep perbandingan
p = 4/(4+3) × 21 = 4/7 × 21 = 4×3 = 12 cm
l = 21 - 12 = 9 cm

luas = p×l = 12 × 9 = 108 cm^2

perbandingan
panjang = 4a
lebar      = 3a

mencari nilai (a)
keliling = 2 x (panjang + lebar)
42 = 2 x (4a + 3a)
42/2 = 4a + 3a 
21 = 7a
a = 21/7
a = 3

panjang = 4a = 4(3) = 12 cm
lebar = 3a = 3(3) = 9 cm

luas persegi panjang = panjang x lebar
L = 12 cm x 9 cm
L = 108 cm²