Math Is Fun Forum

dma251

Member

Registered: 2009-05-17

Posts: 1

Probability question regarding birthdays..... HELP?!?!?!

I have recently discovered that a married couple I am friends with have the same birthdays (same day/month - different years) as my mother and father.   My mother and the other woman share July 26, and my father and the man share April 20th.   

Can anyone tell me what the chances of this occurance are?  We are having a bit of a disagreement over whether it is 365 cubed or 365 squared.     

Also, are there any other facts that matter?  We all lived on the same street, etc?   

Please, I am no math genious here.... I need expert help!

Last edited by dma251 (2009-05-17 18:44:17)

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Probability question regarding birthdays..... HELP?!?!?!

Your question is:

Given that my mother’s birthday is July 26 and my father’s birthday is August 20, what are the chances that two people I know share their birthdays with my parents, one with my mother and the other with my father?

The answer in 1 in 365 squared (ignoring leap years).

If your question is, “What are the chances of four people sharing two birthdays, two of them sharing one birthday and the other two sharing another birthday?” the answer is the same.

Last edited by JaneFairfax (2009-05-17 20:02:17)