Answer:
A
Step-by-step explanation:
Since the triangles are similar then the ratio of corresponding sides = a : b
and ratio of areas = a² : b²
Here the ratio of areas = 7 : 28 = 1 : 4, hence
ratio of sides = [tex]\sqrt{1}[/tex] : [tex]\sqrt{4}[/tex] = 1 : 2
Hence
XY = 2 × DE = 2 × 4 = 8 cm
