Insert one rational number between

$\dfrac{1}{2}$ and 2

As we know that, for any two rational numbers $\dfrac{a}{b}$ and $\dfrac{c}{d}$, $\Big(\dfrac{a + c}{b + d}\Big)$ is also a rational number with its value lying between $\dfrac{a}{b}$ and $\dfrac{c}{d}$.

The rational number between $\dfrac{1}{2}$ and $\dfrac{2}{1}$ is $\Big(\dfrac{1 + 2}{2 + 1}\Big)$

= $\Big(\dfrac{3}{3}\Big)$

=1

Hence, one rational number between $\dfrac{1}{2}$ and 2 is 1.