NIMCET 2009 Question Paper with solutions

Question : 30 of 120

Marks: +1, -0

The probability that a man who is 85 yr old will die before attaining the age of 90 yr is

1 / 3 . A_{1}, A_{2}, A_{3}

and

A_{4}

are four persons who are 85 yr old. The probability that

A_{1}

will die before attaining the age of 90 yr and will be the first to die is

Solution:

Required probability

=P

(atleast one person dies before

90 {yr}) × P

(first person to die is

A_{1}

)

=[1-(\;{2}/{3})^{4}] ×[\;{3 !}/{4 !}]=(1-\;{16}/{81}) × \;{1}/{4}=\;{65}/{324}

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