Picking Colors of Shirts

54 Views Asked by At

If I have a set of 12 shirts comprised of 4 blue, 4 yellow, and 4 red shirts, how many shirts do I have to pick to ensure that there are at least 3 of one color?

1

There are 1 best solutions below

2
On BEST ANSWER

What is the worst case scenario to not have at least three of a color?

When you have somehow picked two red, two blue, and two green shirts

If you pick one more shirt, are you guaranteed three of a color?

More generally, completely ignoring the number of each shirt available (as it is unnecessary information that plays absolutely no role in the solution to the question) the pigeonhole principle says that if you have $n$ objects divided into $k$ categories, you will necessarily have some category with at least $\lceil\frac{n}{k}\rceil$ objects in it.

Here, $k=3$ is the number of categories (the colors of shirts).

What is the smallest $n$ that works (number of shirts to select) so that $\lceil\frac{n}{3}\rceil \geq 3$?