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Another toughie!! :(

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Another toughie!! :(

by GmatKiss » Sat Oct 15, 2011 2:17 pm
A contest will consist of n questions, each of which is to be answered either "True" or "False." Anyone who answers all n questions correctly will be a winner. What is the least value of n for which the probability is less than 1/1000 that a person who randomly guesses the answer to each question will be a winner?

(A) 5

(B) 10

(C) 50

(D) 100

(E) 1,000
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by mbasubrosa » Sat Oct 15, 2011 4:00 pm
probability of answering 1 question right = 1/2.

probability of answering 10 questions right = 1/(2^10) = 1/1024.

Since, 1/1024 is lesser than 1/1000, I would go for B. (n=10).
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