Rational numbers are, by definition, numbers that can be made by dividing two integers. Any number that can be expressed as a fraction is a rational number, for example
"0.5" can be expressed as the quotient between "1" and "2", so it is a rational number
The number "pi", for example, cannot be expressed as a fraction, so it is called an irrational number.
The fraction:
Is the quotient between two whole numbers "4" and "43", so it can be considered a rational number.