Helian Zheng’s countless attempts to get close to Feng Zhiwei are the highlight of episodes 31 – 35, during which Feng Zhiwei holds her ground and repeatedly refuses him by outwardly maintaining her manners but battles him in wits and knowledge at the same time.
One of the test she throws at him (ep. 35) is this good old riddle, which takes Helian Zheng forever to think about but is immediately solved by Ning Yi upon his arrival on the scene.
You have probably come across this riddle while reading an old book or an article somewhere, or have solved it yourself a long time ago. Anyhow, it is not an unpopular riddle. Let’s discuss Feng Zhiwei’s version.
WHAT’S GIVEN?
- Yao Yangyu, Chun Yumeng, and an un-named student each presents a wooden box.
- Only one box contains a piece of chess.
- Each man makes a statement about his box and only one statement is true.
THE QUESTION
Which box contains the stone (chess piece)?
LET’S TAKE A LOOK AT EACH STATEMENT.
Yao Yangyu: “The stone is not in this box” — If Yao Yangyu’s statement is true, then the stone is either in Chun Yumeng or Un-named’s box. But it cannot be in Chun Yumeng’s box because that would make Un-named’s statement also true, which violates the term set by the riddle – only one statement is true. So, the stone is possibly in Un-named’s box.
Chun Yumeng: “The stone is in Yao Yangyu’s box.” — If this statement is true, that makes Yao Yangyu’s statement false and Un-named’s Guy’s statement true. As above, we cannot have two true statements; therefore, Chun Yumeng’s statement is invalid.
Un-named Guy: “The Stone is not in this box.” — If this statement is true, then the stone is not in Un-named’s box, which means it is in either Yao Yangyu’s or Chun Yumeng’s box. But the stone cannot be in Chun Yumeng’s box, because that would make Yao Yangyu’s statement true. The stone also cannot be in Yao Yangyu’s box, because that would mean Chun Yumeng ‘s statement is true. Therefore, Un-named’s statement is invalid.
Without much effort, Ningyi concludes that Yao Yangyu is telling the truth and the stone is in Un-named Guy’s box.