2278. Percentage of letters in string

problem ：

  Why? , When in the code times Variable is float The type is , perform case You get the wrong results ？

class Solution {
public:
    int percentageLetter(string s, char letter) {
        //  Floating point numbers are used here , It is convenient to divide floating-point numbers 
        /* Note:
           If you use float Type change the result to int Time will lead to the result minus one 
          case： times = 59; size = 100, return 58
        */
        //  The number of times letters appear   
        double times = 0;
      
        for(int i = 0; i < s.size(); i++){
          if(s[i] == letter){
            times++;
          }  
        }
      
        //  Expand the results 100 The decimal part is removed again , This requires downward evidence 
        return (int)((times/s.size())*100);
    }
};