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# A lottery ticket vendor sells lottery tickets that, when

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GMAT Instructor
Joined: 04 Jul 2006
Posts: 1268
Followers: 23

Kudos [?]: 148 [0], given: 0

A lottery ticket vendor sells lottery tickets that, when [#permalink]  09 Jul 2006, 03:32
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
A lottery ticket vendor sells lottery tickets that, when scratched, reveal whether or not the holder has won a prize. If each ticket has a 25% chance of carrying a prize, what is the lowest number of tickets that Diane could but that would ensure that grandmother would have at least a 75% chance of experiencing the thrill of winning a prize?

(A) 5 (B) 6 (C) 8 (D) 9 (E) 10
GMAT Instructor
Joined: 04 Jul 2006
Posts: 1268
Followers: 23

Kudos [?]: 148 [0], given: 0

Maybe if I gave granny a name, people would try the problem. Let's call her Della.
Manager
Joined: 04 Jul 2006
Posts: 57
Followers: 1

Kudos [?]: 2 [0], given: 0

The formula for not winning with n lottery tickets is (1-1/4)^n=3/4^n^=(3/2^2)^n. This must be smaller than 1/4.
n=5: (3/4)^5=243/1024 < 256/1024=1/4

Therefore, (A) is the correct answer.
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