Question

What is the probability that two people selected at random have the same birthday? Ignore leap years. 1/365 2/365 1/133,225

Answer 1

Answer:  The correct option is (A) $\dfrac{1}{365}.$

Step-by-step explanation:  We are given to find the probability that two people selected at random have the same birthday.

Since there are 365 days in a non-leap year, so we will be considering the number of days as 365.

Now, whatever be the birth day of the first person, we need to select another person that has the same birth day as the first one.

Let, 'E' be the event that the second person has the same birthday as the first one.

So, n(E) = 1, because the birthday can be only one day out of 365 days.

Let, 'S' be the sample space for the experiment.

So, n(S) = 365.

Therefore, the probability  the second person has the same birthday as the first one will be

$P(E)=\dfrac{n(E)}{n(S)}=\dfrac{1}{365}.$

thus, the required probability is $\dfrac{1}{365}.$

Option (A) is correct.

Answer 2

I think it must be  1/365

It does not matter what the first persons birthday is - you just have to choose another one with same birthday and you have 365 days to choose from. ( I guess we can ignore a leap year).