c# - Check how many instances of strings in a list

Well I enquired about checking if certain keywords can be found in an list and if they are all there the question is correct. Found here: Check if the string contains all inputs on the list

What I would like to also know is how many of the words are in the list, then divide it and get a percentage, so the user knows how accurately they answered each question.

        public String KeyWords_Found()
        {
            int Return_Value = 0;
            foreach (String s in KeyWords)
            {

                if (textBox1.Text.Contains(s))
                {
                    Return_Value++;
                }
            }
            int Holder = Return_Value / KeyWords.Count;
            int Fixed = Holder * 100;
            return  Fixed + "%";
        }

So what I want that code it do is check for all instances of keywords listed into the list KeyWords. Then get the percentage by dividing by the total amount of keywords and multiplying by 100. But it says that both values are 0 and i cant divide by 0. I'm not sure why they would be zero. Confused! Help!