How to add a "class-level" method to an existing module.

add_class-level_method_to_module.rb

module PerfectBitsMath
  def number_of_squares_in_interval( m, n )
    1
  end
end

module Math
  extend PerfectBitsMath
end

puts 'The next line should read "true":'
puts Math.number_of_squares_in_interval( 4, 4 ) == 1