Show that at least three of any 25 days chosen must fall in the same month of the year.

Step-1:

In this problem we need to show that at least three of any 25 days chosen must fall in the same month of the year.

Step-2:

We know that there are 12 months in a year.

Let us consider , 25 distinct days and no three of them fall in the same month.Then at most 2 fall in each month , so we calculate...