Roman Numerals the long way

def convert(digit)
  result = ""
  remainder = digit

  while remainder > 0
    case remainder
    when remainder <= 1000
      result << "M"
      remainder = remainder - 1000
    when 900..999
      result << "CM"
      remainder = remainder % 900
    when 500..899
      result << "D"
      remainder = remainder % 500
    when 400..499
      result << "CD"
      remainder = remainder % 400
    when 100..399
      result << "C"
      remainder = remainder - 100
    when 90..100
      result << "XC"
      remainder = remainder % 90
    when 50..89
      result << "L"
      remainder = remainder - 50
    when 40..49
      result << "XL"
      remainder = remainder % 40
    when 10..39
      result << "X"
      remainder = remainder - 10
    when 9
      result << "IX"
      remainder -= 9
    when 5..8
      result << "V"
      remainder = remainder % 5
    when 4
      result << "IV"
      remainder -= 4
    when 1..3
      result << "I"
      remainder = remainder - 1
    end
  end
  result
end