Find a rational number between 3 and 7 using the mean method.

If a and b are two rational numbers, then $\frac{\mathrm{a}+\mathrm{b}}{2}$is a rational number between a and b such that a < $\frac{\mathrm{a}+\mathrm{b}}{2}$  < b.

The mean of 3 and 7 is $\left(\frac{{\displaystyle 3}+{\displaystyle 7}}{2}\right)=\frac{10}{2}$$=5$

Therefore, 5 is a rational number between 3 and 7.