place.rb

class Integer
  def place
    case self % 10
    when 1
      "#{self}st"
    when 2
      "#{self}nd"
    when 3
      "#{self}rd"
    when 4..9, 0
      "#{self}th"
    end
  end
end
(1..100).each do |x|
  puts x.place
end