Let the edge length of larger cube = A
and the edge length of smaller cube = a
Total volume will remain constant
Volume of larger cube = 27 × Volume of smaller cube
A³ = 27 × a³
Cube root on both sides
A = 3 a
A : a = 3 : 1
Ratio of surface area
= 6 × A² : 6 × a²
= A² : a²
= 9 : 1
∴ Ratio of their surface area is 9 : 1