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# A group of N students will be randomly seated in a row of N chairs. What is the probability that Beth, one of the students, will be at the extreme right-hand end of the row?

Difficulty: Sub-600 Level, Probability, Data Sufficiency (DS)

Monday 25 July 2022,

A group of N students will be randomly seated in a row of N chairs. What is the probability that Beth, one of the students, will be at the extreme right-hand end of the row?

(1) N is an odd prime number
(2) the probability that Steve, another one of the students, is at the extreme left-hand end of the row is 1/13

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EXPLANATION:

(i) We just know that N is odd and prime. it can be any no. 5,7 etc >> not sufficient.
(ii) Any other student on the right > P = 1/13

P of Beth is on the right 1 - P of any other child on right = 1- 1/13