Question

Usha and Aastha are two friends. What is the probability that their birthday falls on the same day 14 November 2015?

Answer 1

Usha may have any one of the 365 days on the year 2015 as her birthday. Similarly Aastha may have any one of the 365 days of the year 2015 as her birthday.

Total number of outcomes in which Usha and Aastha may have their birthday= 365 × 365
Usha and Aastha may have same birthday on any one of the 365 Days Of The Year 2015.

Number of favourable outcomes in which Usha and Aastha will have same birthday= 365

Probability that both have same birthday= 365/(365×365)= 1/365.

Hence,the  probability  that their birthday falls on the same  day 14 November 2015 = 1/365.

HOPE THIS WILL HELP YOU...

Answer 2

out of Usha and Astha one may have his birthday on any of the 365 days of the year.... but the other can not have her birthday on the same day...

total no of outcomes = 365

no of favourable outcomes = 365 - 1 = 364

[probability = fav no of outcomes / total no of outcomes ]

probability of having birthday on different days = 364 / 365

probability of having Birthday on same day =
1 - 364/ 365
= 1/ 365......

[ P ( not E) = 1 - P( E) ]