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The probability of meeting a random person who has the same birthday as you is365• whichis approximately 0.27%. What is the probability that the 25th person you meet is the firstperson who has the same birthday as you?00.27%00.14%00.25%00.03%

User Edward J Beckett
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1 Answer

16 votes
16 votes

Given:

The same birthday probability is


\begin{gathered} =(1)/(365) \\ \\ =0.27\% \end{gathered}

Find:-

Person who has the same birthday

Explanation-:

The probability of meeting a random person who has the same birthday is:


=(1)/(365)

Probability of meeting a random person who does not has same birthday as you


\begin{gathered} =1-(1)/(365) \\ \\ =(365-1)/(365) \\ \\ =(364)/(365) \end{gathered}

The required probability that the 25th person you meet is the first person who has the same birthday as


\begin{gathered} =\text{ Probability that the first 24 persons we meet did not have same birthday \rparen}*(\text{ probability that the first 25 person we meet has same birthday\rparen} \\ \end{gathered}

Therefor,


\begin{gathered} P=((364)/(365))^(24)*(1)/(365) \\ \\ =(0.9972)^(24)*0.27 \\ \\ =0.9362*0.27 \\ \\ =0.25\% \end{gathered}

User Puggsoy
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