If △ABC ∼ △DEF such that 2AB = DE and BC = 8 cm, then the length of EF is:

16 cm

As the ratio of corresponding side of similar triangle is equal,

Therefore,

As, \(\Delta \)ABC is similar to \(\Delta \)DEF

⇒ \(\frac{AB}{DE}\) = \(\frac{BC}{EF}\)

⇒ As we know, 2AB = DE

⇒ \(\frac{AB}{2AB}\) = \(\frac{8}{EF}\)

⇒ EF = 8 x 2 = 16 cm.

Therefore, the value of EF is 16 cm.