Broken Window

One snowy night, Sherlock Holmes was in his house sitting by a fire. All of a sudden a snowball came crashing through the window, breaking it. Holmes got up and looked out just in time to see three neighborhood kids who were brothers run around the corner. Their names were John Crimson, Mark Crimson, and Paul Crimson.

The next day Holmes got a note on his door that read:

“? Crimson. He broke your window.”

Which of the three Crimson brothers should Sherlock Holmes question about the incident?

He should question Mark. The note read: “QUESTION MARK Crimson. He broke your window.”

WWII Planes

During World War II, the mathematician Abraham Wald was asked to help with determining which parts of the allied forces’ planes must be armored better. After examining the surviving American planes, he noticed that there were many holes in the fuselage, and very few in the engines. After careful thinking, he suggested that the armor on the engines must be improved. Why?

Abraham Wald realized that the holes should have been distributed more evenly across the planes. Therefore the planes which had more holes in the fuselage survived, while the planes which had more holes in the engines got destroyed.