### Theory:

Between any two rational numbers, there are countless or infinite rational numbers.

Find the rational number between $\frac{2}{10}$ and $\frac{8}{10}$.
Example:

Now, $\frac{3}{10}$, $\frac{4}{10}$, $\frac{5}{10}$, $\frac{6}{10}$, $\frac{7}{10}$ are rational numbers between $\frac{2}{10}$ and $\frac{8}{10}$.

The number of these rational number between $\frac{2}{10}$ and $\frac{8}{10}$ is $$5$$.

We can also write $\frac{2}{10}$ as $\frac{20}{100}$ and $\frac{8}{10}$ as $\frac{80}{100}$

Now, $\frac{21}{100}$, $\frac{22}{100}$, $\frac{23}{100}$, $\frac{24}{100}$, ……$\frac{78}{100}$, $\frac{79}{100}$ are rational number between $\frac{2}{10}$ and $\frac{8}{10}$.

The number of these rational number between $\frac{21}{100}$ and $\frac{80}{100}$ is $$59$$.

And also can express $\frac{2}{10}$ as $\frac{2000}{10000}$ and $\frac{8}{10}$ as $\frac{8000}{10000}$

Now, $\frac{2001}{10000}$, $\frac{2002}{10000}$, $\frac{2003}{10000}$$\frac{2004}{10000}$, . . . , $\frac{7998}{10000}$, $\frac{7999}{10000}$ are rational number between $\frac{2}{10}$ and $\frac{80}{100}$.

Thus, we get $$5999$$ rational numbers between $\frac{2000}{10000}$ and $\frac{8000}{10000}$.