Question:
Find four rational numbers between $\frac{3}{7}$ and $\frac{5}{7}$.
Solution:
n = 4
n + 1 = 4 + 1 = 5
$\frac{3}{7}=\frac{3}{7} \times \frac{5}{5}=\frac{15}{35}$
$\frac{5}{7}=\frac{5}{7} \times \frac{5}{5}=\frac{25}{35}$
Thus, rational numbers between $\frac{3}{7}$ and $\frac{5}{7}$ are $\frac{16}{35}, \frac{17}{35}, \frac{18}{35}, \frac{19}{35}$.