Practice By Tag: COMP 2804: Discrete Structures II
Question: 2014 Winter Midterm - 161 .
Consider three people, each one having a uniformly random birthday (out of 365 days; we ignore leap
years). What is the probability that at least two of them have the same birthday?
(a)
$1 - \frac{364 \cdot 363}{365^2}$
(b)
$1 - \left. {3 \choose 2} \middle/ 365^3 \right.$
(c)
$1 - \left. \bigl\{ {3\choose 2} + {3 \choose 3} \bigr\} \middle/ 365^3 \right.$
(d)
$1 - \frac{365^2}{364 \cdot 363}$