Рац. числа - 1 точка

 class Rational
    {
        int num;
        int den;
        public Rational (int n, int d)
        {
            this.num = n;
            this.den = d;
        }
        public void print()
        {
            Console.WriteLine("{0}/{1}", this.num, this.den);
        }
        public void multi(Rational r)
        {
            this.num *= r.num;
            this.den *= r.den;
        }
        public void sum(Rational r)
        {
            this.num = this.num * r.den + r.num * this.den;
            this.den *= r.den;
        } 
        public void sub(Rational r)
        {
            this.num = this.num * r.den - r.num * this.den;
            this.den *= r.den;
        }
        public void dev(Rational r)
        {
            this.num *= r.den;
            this.den *= r.num;
        }
    }
    class Program
    {
        static void Main(string[] args)
        {

            Rational p = new Rational(1, 2);
            Rational c = new Rational(1, 3);
            Console.WriteLine("Действието е умножение.");
            p.print();
            c.print();
            p.multi(c);
            p.print();

        }
    }
}