Suppose there are 4 people and each person has an associated birth month. How many ways are there so that at least 2 people share the same birth month?
My first instinct is that it's $12\cdot12\cdot11\cdot10$ but that doesn't seem right.
Suppose there are 4 people and each person has an associated birth month. How many ways are there so that at least 2 people share the same birth month?
My first instinct is that it's $12\cdot12\cdot11\cdot10$ but that doesn't seem right.