Answer: 
 
4 : 2 
 
Step-by-step explanation: 
 
We are given ΔABC ≅ ΔA'B'C'. 
 
When two triangles are congruent, their corresponding sides and angles are congruent. 
 
Since, the sides of the triangles are in relation, 
 
AB = 2 × A'B' and side BC = 2 × B'C' i.e. 4 = 2 × 2 and 9 = 2 × 4.5. 
 
Therefore, the ratio of the corresponding sides are given by 4 : 2 and 9 : 4.5 i.e. 2 : 1. 
 
Since, the ratio of the corresponding sides comes out to be 2 : 1 = 4 : 2. 
 
Hence, the ratio of the corresponding sides is 4 : 2.