Question

How large must a group of people be in order to guarentee that there are at least two people in the group whose birthdays fall in the same month

Answer 1

13

Explanation:

This problem is an example of pigeonhole principle which states that If n+ 1 objects are placed into n boxes, then some box contains at least 2 objects.

Here no. of months in a year are boxes n = 12.

Therefore number of objects( people) = n+1= 13.

Then,at least two people in the group whose birthdays fall in the same month.