Label the magnitudes of a number.

number_magnitude.rb

def labelize number
  magnitudes = [
    [1e12.to_i, 'trillion'], [1e9.to_i, 'billion'], [1e6.to_i, 'million'],
    [1e3.to_i, 'thousand'], [1e2.to_i, 'hundred']
  ]

  left = number
  magnitudes.each do | label |
    if left / label[0] > 0
      write = left / label[0]
      left  = left - write * label[0]
      puts write, label[1], left
    end
  end
end

labelize 999999