# If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23. # Find the sum of all the multiples of 3 or 5 below 1000.

multiples_challenge.rb

class Challenges
  # www.projecteuler.net
  # If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
  # Find the sum of all the multiples of 3 or 5 below 1000.
  def multiples_of_3_and_5
    (1...1000).select { |n| n if (n % 3 == 0) || (n % 5 == 0) }.inject(:+)
  end
end

puts "challenge 1: #{Challenges.new.multiples_of_3_and_5}"