Given that ΔABC and ΔDEF are similar triangles such that AB = 3 cm, DE = 3 cm, DF = 2.5 cm and EF = 2 cm.

We know that two triangles are similar if their corresponding sides are proportional.

First consider,

⇒ AB = 6 cm … (1)

Now,

⇒ CA = 5 cm … (2)

Then, perimeter of ΔABC = AB + BC + CA = 6 + 4 + 5

∴ Perimeter of ΔABC = 15 cm