Question
Fri February 13, 2009 By:

probability _atleast one post-atleast two posts

Expert Reply
Mon February 16, 2009

prob of being selected at first post = p1 = 1/5

similarly for second post = p2 = 1/4

and for third = p3 = 1/6

prob that he will be selected for atleast one post

=1 - (he is not selected at any post)

=1 - (1-1/4) ( 1-1/5) (1-1/6)

=1 - 3.4.5/4.5.6 = 1/2

prob that he will be selected for at least two posts

=p1.p2(1-p3) + (1-p1).p2.p3 +(1-p2).p1.p3

=(3+4+5) / 4.5.6

=1/10

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