is 3.10723 rational
Yes, it is a rational number; decimal.
Yes it is rational.
This is because it can be expressed as a fraction 3.10723 is also 3 10723/100000
note: not all decimals are rational, pi is an example of an irrational decimal.
A decimal is rational if it terminates or if it repeats indefinitely. The decimal fits the first condition and is, therefore, rational.