Answer to Question #384 in Statistics and Probability for madcat
The letter is in the table with the probability p. Moreover it can equiprobably be in any of the 8 boxes of the table. We have checked 7 boxes and didn’t find the letter there. What is the probability that the letter is in the 8th box?
In this case, the event “the letter is in the table” is equivalent to the event “the letter is in the 8th box”, which means that the probability of finding the letter in the 8th box is equal to the probability of finding a letter in the table and it is p.