diketahui panjang AE= 8 cm dan BD = 30 cm jika luas layang-layang abcd adalah 420 cm² keliling layang-layang tersebut... cm pakai cara yaa!!!

d1 = (8 + EC)cm
d2 = 30cm
L = 420cm^2

L = d1 × d2 / 2
420 = (8 + EC) × 30 / 2
840 = 240 + 30EC
30EC = 600
EC = 20cm

K = jumlah 4 sisi miring

s1^2 = 8^2 + 15^2
s1^2 = 64 + 225
s1^2 = 289
s1 = 17cm

s2^2 = 20^2 + 15^2
s2^2 = 400 + 225
s2^2 = 625
s2 = 25cm

s1 = s3
s2 = s4

K = s1 + s2 + s3 + s4
K = 17 + 25 + 17 + 25
K = 84cm (B)