It is given that ΔABC $$sim$$ ΔDEF Also, length of AB = 18 cm and length of the corresponding side DE = 10 cm => Ratio of Perimeter of ΔABC : Perimeter of ΔDEF = Ratio of corresponding sides = AB : DE = $$frac{18}{10} = frac{9}{5}$$ $$ herefore$$ The required ratio is 9 : 5 => Ans - (B)