10 votes 10 votes The probability that two friends are born in the same month is ____ ? $1/6$ $1/12$ $1/144$ $1/24$ Probability probability isro2014 + – ajit asked Aug 15, 2015 • edited Dec 8, 2022 by Lakshman Bhaiya ajit 7.4k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
Best answer 29 votes 29 votes Let us say that what is the probability that they are not born in same month? A can be born in any of 12 months and B can be born in any of the remaining 11 months $\Rightarrow$ Total possible cases = 12 x 11 = 132 Total Sample space with us : 12 x 12 = 144 $\Rightarrow$ The probability that they are not born in same month = $\frac{132}{144}$ $\Rightarrow$ The probability that they are born in the same month $1 - \frac{132}{144} = \frac{12}{144} \Rightarrow \frac{1}{12}$ Alternatively, Let the first friend be born in any of the 12 months. For the second friend we have 12 cases and only 1 is favorable. So, probability = $\frac{12}{12} \times \frac{1}{12} \implies \frac{12}{144} \implies \frac{1}{12}$ Mojo-Jojo answered Aug 18, 2015 • edited May 11, 2016 by Mojo-Jojo Mojo-Jojo comment Share Follow See all 0 reply Please log in or register to add a comment.
7 votes 7 votes $Total\ outcomes = 12*12 =144$ $Favourable\ outcomes = \{$ (Jan,Jan) , (Feb,Feb), (March,March)....(Dec, Dec)$\} = 12$ $Probability = \frac{ Favourable\ outcomes}{Total \ Outcomes} = \frac{12}{12*12} = \frac{1}{12}$ $\therefore$ $B.$ is correct Satbir answered Jan 6, 2020 Satbir comment Share Follow See all 3 Comments See all 3 3 Comments reply `JEET commented Jan 6, 2020 reply Follow Share Total outcome, why not $12C_2$? 0 votes 0 votes Satbir commented Jan 6, 2020 reply Follow Share Since both are Independent events. 0 votes 0 votes `JEET commented Jan 6, 2020 reply Follow Share Yes, right. 0 votes 0 votes Please log in or register to add a comment.
1 votes 1 votes B) 1/12 Pranay Datta 1 answered Aug 15, 2015 Pranay Datta 1 comment Share Follow See all 3 Comments See all 3 3 Comments reply ajit commented Aug 15, 2015 reply Follow Share how? 0 votes 0 votes Pranay Datta 1 commented Aug 15, 2015 reply Follow Share Desire outcome/ total outcome = probability total outcome = 12*12 (say if a born in jan then b may born any of the 12 months , if a born in feb then b may born any of the 12 months like wise for 12 months there are 12*12 combination ) Desire outcome = 12 (say if a born in jan then b have to born in jan only one way ,if a born in feb then b have to born in feb only one way, like wise for 12 months there are 12 ways ).peace 4 votes 4 votes ajit commented Aug 15, 2015 reply Follow Share thanks 0 votes 0 votes Please log in or register to add a comment.