ΔABC is similar to ΔDEF. If the sides of ΔABC, that is AB, BC and CA, are 3, 4 and 5 cms respectively, what would be the perimeter of the ΔDEF, if the side DE measures 12 cms ?

Perimeter of ΔABC
= 3 + 4 + 5
= 12
$$\eqalign{ & \frac{{{\text{Perimeter}}\,{\text{of}}\,\vartriangle ABC}}{{{\text{Perimeter}}\,{\text{of}}\,\vartriangle DEF}} = \frac{{AB}}{{DE}} \cr & \frac{{12}}{{{\text{Perimeter}}\,{\text{of}}\,\vartriangle DEF}} = \frac{3}{{12}} \cr} $$

Perimeter of ΔDEF = 48 cms