Simple calculation of probability

This is the same as in the lucky draw. For example, if the black ball is considered as the winning bid, the white ball will not win the prize.

At this time, we all smoked, but everyone didn't say what they smoked, so the probability of everyone smoking was110.

For example, if someone has already smoked, I will smoke at this time.

Then my probability of winning the prize is p = (110) * 0+(9/10) * (1/9).

Where (110) * 0 means that the first person won the prize, and my probability of winning the prize is obviously 0.

(9/ 10)*( 1/9) indicates the probability that the first person will not win the prize, because 10 balls have been drawn, leaving only 9 balls.

So the winning probability is not110, but 1/9.

And because it is an independent repeated event, multiplication is used.