Question

Diketahui luas belah ketupat 600cm.jika perbandingan panjang diagonal-diagonalmya adalah 4:3,maka keliling belah ketupat tersebut adalah?

Answer 1

D1 = 4a
d2 = 3a

L = 1/2 x d1 x d2
600 = 1/2 x 4a x 3a
600 x 2 = 12a
1200 = 12 a
1200 / 12 = a
100  = a

d1 = 4a ->> 4 (100) = 400 cm
d2 = 3a ->> 3(100) = 300 cm

Answer 2

Luas = d1 x d2 x 1/2
600 = 4y x 3y x 1/2
600x 2 = 4y x 3y
1200 = 12y²
y² = 1200/12
y² = 100
 y = √100
y = 10

d1 = 4y = 4 x 10 = 40 cm
d2 = 3y = 3 x 10 = 30 cm

cari sisi
√(40:2)²+(30:2)²
√20²+15²
√400 + 225
√625
=25 cm

keliling = 4s 
keliling = 4 x 25 cm
keliling = 100 cm