euler/euler001.rb

def multiples_of_three_and_five_below(n)
  multiples = []
  (3..n-1).each do |i|
    multiples << i if ((i % 3 == 0) || (i % 5 == 0))
  end
  multiples
end

puts multiples_of_three_and_five_below(1000).inject(:+)