Probability question on raffle

[BrownianMan]

1 (a) A bookstore has a draw for a $25 book certificate. Each customer draws a ticket from a bowl of 100 tickets. Only one of the tickets is a winning ticket and once the certificate is won, the draw is over. If the tickets are drawn with replacement, what is the probability that the winner is one of the first 10 customers?
(b) If the tickets in part (a) are drawn without replacement, what is the probability that the winner occurs no later than the 99th customer?

Any hints on how to get started?

 

[deluks917]

The easiest way to do this problem is to calculate the odds the lottery goes on for more then ten rounds and use this to get the probability you want. The odds anyone person does not draw the winning ticket (at any point in the lottery) is 99/100. What are the odds ten people all don't win?

 

[BrownianMan]

For part a) I get 0.0956. Is this right?

For part b) wouldn't the probability that the second person doesn't win be 98/99, since the tickets are drawn without replacement?

 

[deluks917]

Your first answer is correct. I'm sorry about the second question. You have the right idea for the second problem when you multiply the probibilities lots of terms should cancel.