Savita and Hamida are friends. What is the probability that both will have:
(i) Different birthdays
(ii) The same birthday (ignoring a leap year)
Solution:
There are 365 days in a year, so Savita’s birthday can be any of these days. Hamida’s birthday can also be any of the 365 days.
(i) If Hamida’s birthday is different from Savita’s, there are 364 days left for her birthday.
So, the probability that Hamida has a different birthday is:
P(different birthdays) = 364/365
(ii) The probability that they have the same birthday is:
P(same birthday) = 1− P(different birthdays) = 1/365