def first_digit
      if @numbers.size == 9
        value = 0
        multipliers = [10,9,8,7,6,5,4,3,2]

        multipliers.each_with_index do |mult, index|
          value += @numbers[index].to_i * mult
        end

        check_remainder(value % 11)
      end
    end
def first_digit
      if @numbers.size == 9
        value = 0
        multipliers = [10,9,8,7,6,5,4,3,2]

        multipliers.each_with_index do |mult, index|
          value += @numbers[index].to_i * mult
        end

        check_remainder(value % 11)
      end
    end
Gera o primeiro dígito verificador