Puzzle o' the Day 410!
In grad school, I once entered a classroom to find this puzzle; Professor Dantzig (who was just leaving) had left it on the blackboard. Can you solve it? I bet Dantzig would still give you extra credit.
Posit a world where every pair of people is either friends or enemies. It's not hard to show that if you have six people at a party, then there must be either a group of three where every pair is friends, or a group of three where every pair is enemies.
How many people must you have at the party to guarantee that there's either a group of five where every pair is friends, or a group of five where every pair is enemies?
Posit a world where every pair of people is either friends or enemies. It's not hard to show that if you have six people at a party, then there must be either a group of three where every pair is friends, or a group of three where every pair is enemies.
How many people must you have at the party to guarantee that there's either a group of five where every pair is friends, or a group of five where every pair is enemies?