One can use this code to generate random questions which is returned in a text format and shall be converted to image form and validate the answer response with the answer. Test run this code at http://www.programr.com/Ruby/IntelligentCaptcha

IntelligentCaptcha.rb

class Captcha
  def initialize 
    @numbers=[1,2,3,4,5,6,7,8,9] 
    @numbers_alpha={ 
      1 => "one",
      2 => "two",
      3 => "three",
      4 => "four",
      5 => "five",
      6 => "six",
      7 => "seven",
      8 => "eight",
      9 => "nine"
    }
    @ops={
      "+" => "plus",
      "-" => "minus",
      "*" => "multiplies",
      "/" => "divided by"
    }
  end
  def array

    digit1=@numbers[rand(9)] 
    digit2=@numbers[rand(9)] 
    op=@ops.keys[rand(4)] 

    val = eval "#{digit1}#{op}#{digit2}" 
    captcha_text = "#{@numbers_alpha[digit1]} #{@ops[op]} #{@numbers_alpha[digit2]}" #

    return val,captcha_text 

  end

end
a=Captcha.new.array
puts a.inspect