Returning void from method to prevent execution

I am attempting to exit a method which returns void after checking a condition (I realize this would be easier if I threw an exception, but I'm trying to avoid that for this project). I have the code below, which should return out of the if statement, if I am interpreting it correctly, but the entire method is still executing. Is there a problem in the code somewhere (I can post more if needed), or is there a better way to write this without exception handling?

void Rational::divide(Rational b) {
    if ((double)b.numerator/(double)b.denominator == 0) {
        cout << "Denominator cannot be zero." << endl;
        return;
    }
    numerator = numerator * b.denominator;
    denominator = denominator * b.numerator;
    reduce();
}