Roman numerals converter

roman_numerals.rb

# solution from https://www.codewars.com/kata/reviews/51b62bf7a9c58071c6000026/groups/560d5575e3ff138f6400001d

NUMS = [
  [1000, "M"],
  [900, "CM"],
  [500, "D"],
  [400, "CD"],
  [100, "C"],
  [90, "XC"],
  [50, "L"],
  [40, "XL"],
  [10, "X"],
  [9, "IX"],
  [5, "V"],
  [4, "IV"],
  [1, "I"]
]


def solution num
  str = ""
  NUMS.each do |number, sub|
    while num >= number
      str << sub
      num -= number
    end
  end
  str
end