modules.rb

module Calculator
  def add(n)
    self + n
  end

  def subtract(n)
    self-n
  end

  def multiply_by(n)
    self * n
  end

  alias :multiply :multiply_by

  def divided_by(n)
    self.to_f / n
  end

  alias :divide :divided_by

end

class Numeric
  include Calculator
end