If Δ ABC and Δ DEF are similar such that 2AB = DE and BC = 8 cm, then Find EF

Two triangles $∆$ABC and $∆$DEF are said to be similar if their corresponding sides are proportional.
i.e. 

$\frac{AB}{DE}= \frac{BC}{EF}= \frac{AC}{DF}$

2AB = DE

2BC = EF

⇒ 2×8 = EF

⇒ EF = 16 cm