The product of a rational number and its reciprocal is            

If $\text{'}a\text{'}$ is any rational number and the reciprocal of  $\text{'}a\text{'}$ is $\frac{1}{a}$

The product of a rational number and its reciprocal is $a\times \frac{1}{a}=1$

  Example : $5\in Q$

The reciprocal of  5 is $\frac{1}{5}$

The product of  5 and $\frac{1}{5}=5\times \frac{1}{5}$

                                         $=1$     (  1 is called multiplicative identity )