rand_text.rb

words = {
  'hello' => 100,
  'world' => 50,
  'this' => 200,
}

storage = {}
sum = 0

words.each do |word, weight|
  top = sum + weight
  storage[(sum..top)] = word
  sum = top
end

100.times do
  r = rand(sum)
  p storage.find{|range, word| range.include?(r) }
end