One box contains two gold balls, another box contains two silver balls, and the final box contains one gold ball and one silver ball.”Obviously in the real experiment the boxes should not be see-through. “You put your hand in and take a ball […] it’s a gold ball. After all, the question says you took a gold ball first – meaning you’re dealing with only box A or box B. That means that, if you draw out a gold ball, there are actually three potential balls left over: a silver ball in box B, a gold ball in box A, or the other gold ball in box A. That means that the chance of picking a silver ball is now one out of three – just 33 percent.