Question

What is the probability that a husband, wife, and daughter have the same birthday? Ignore leap years.

Answer 1

Answer:

$\frac{1}{365}^{2}$= 7.50* $10^{-6}$

Explanation:

The birthday of the husband, wife, and daughter is an independent event that won't influence each other probability. Then, to find the probability you need to multiply each chance of these events.

Everyone has 1 birthday out of 1 year and every nonleap year has 365 days. So, the chance for having same birthday is 1/365.  We need all three to have the same birthday, so we can pick one person's birthday and then calculate the chance that two others have that birthday too.  

In another word, just calculate the chance that wife and daughter(2 people) have the same birthday as the husband. The calculation will be:

1 * $\frac{1}{365}$ * $\frac{1}{365}$ = $\frac{1}{365}^{2}$= 7.50* $10^{-6}$