4. Rational numbers

• A rational number is a number that can be expressed as a fraction

      n / d
  

  where n and d are integers and d != 0.

• Thus, a rational number n/d is said to have numerator n and denominator d.

• Denominator is usually kept strictly positive.

• Rational numbers can simplified (normalized or reduced) in case when the numerator and denominator has one or more common factors.