Coin changes solved by recursion

coin_change.rb

def coin_change(coins, amount)
	coins = coins.sort
	coin = coins.first
	multiples = (0..(amount / coin)).map{|division| division * coin}
	solution = amount

	if coins.count == 1
		if amount % coin != 0
			return -1
		else
			return amount / coin
		end
	else
		coins.shift
		multiples.each_with_index do |multiple, index|
      if index < solution
        result = coin_change(coins, amount - multiple)
        if result != -1
          solution = [index + result, solution].min
        end
      end
		end
  end
	solution == amount ? -1 : solution
end

puts "#{coin_change([470,35,120,81,121], 9825)}"