Perguntas de entrevista de vagas de Financial Software Developer Intern da empresa Bloomberg

You have 50 coins in a dark room and you cannot see the coins, only feel them. You know there are 30 heads, and 20 tails. How can you split up the coins into two groups and guarantee that both piles have the same amount of tails? You cannot determine the side of the coin by touch and you are allowed to flip coins if you want to.