A rectangle is divided into a certain number of equal parts. If 16 of the parts so formed represents the fraction $\dfrac{2}{5}$, find the number of parts in which the rectangle has been divided.

Let the total number of parts be x.

Given, 16 parts represent the fraction $\dfrac{2}{5}$.

$\Rightarrow \dfrac{16}{x} = \dfrac{2}{5}\\[1em] \Rightarrow 16 \times 5 = 2 \times x\\[1em] \Rightarrow 80 = 2x\\[1em] \Rightarrow x = \dfrac{80}{2}\\[1em] \Rightarrow x = 40$

Hence, the rectangle is divided into 40 equal parts.