A Probability Idiot Problem

The so-called probability of drawing becomes greater, which is said only when the previous person did not draw it. As long as the previous person draws it, the probability of drawing it himself must be 0.

The probability of success or failure cannot be regarded as "this is an option", "this is an option" and "one of the two options occurs, so the probability is 1/2", which is completely wrong. For example, "I was either elected president of the United States in the 20 12 general election, or I was not elected president of the United States", obviously it cannot be said that the probability of being elected is 1/2. In fact, this probability is basically zero.

The probability of the first person winning the prize is 1/4, which is very simple.

The second person won the prize on the basis that the first person didn't win the prize, so the probability should be 1/3*3/4= 1/4.

The third person won the prize on the basis that the first two people didn't win, so the probability should be 1/2*2/3*3/4= 1/4.

So the probability is 1/4. As for the topic that the probability of winning the prize is gradually increasing, it is wise after the event. The third person will be nervous before his turn.