$$\triangle$$ABC $$\sim$$ $$\triangle$$DEF and the area of $$\triangle$$ABC is 13.5 cm$$^2$$ and the area of $$\triangle$$DEF is 24 cm$$^2$$ . If BC = 3.15 cm, then the length (in cm) of EF is:

$$\triangle$$ABC $$\sim$$ $$\triangle$$DEF

$$\Rightarrow$$  $$\frac{\text{Area of triangle ABC}}{\text{Area of triangle DEF}}$$ = $$\left(\frac{BC}{EF}\right)^2$$

$$\Rightarrow$$  $$\frac{13.5}{24}=\left(\frac{3.15}{EF}\right)^2$$

$$\Rightarrow$$  $$\frac{135}{240}=\left(\frac{3.15}{EF}\right)^2$$

$$\Rightarrow$$  $$\frac{9}{16}=\left(\frac{3.15}{EF}\right)^2$$

$$\Rightarrow$$  $$\frac{3.15}{EF}=\frac{3}{4}$$

$$\Rightarrow$$  EF = 4.2 cm

Hence, the correct answer is Option D