(N/A) number is rational if it can be expressed in the form $\frac{p}{q}$,where $p$ and $q$ are integers and $q \ne 0$.
Given the number $3.142678$,we can remove the decimal point by dividing by the appropriate power of $10$.
Since there are $6$ digits after the decimal point,we multiply and divide by $1,000,000$.
$3.142678 = \frac{3142678}{1000000}$.
This fraction can be simplified by dividing both the numerator and the denominator by their greatest common divisor,which is $2$.
$\frac{3142678 \div 2}{1000000 \div 2} = \frac{1571339}{500000}$.
Since $1571339$ and $500000$ are integers and $500000 \ne 0$,the number $3.142678$ is a rational number.