Here are three little puzzles that were put to me by a random old man I got chatting to on the train whilst I was back in the UK last week. The conversation got started when he noticed that I was reading a book in Norwegian (Jo Nesbø's The Bat (Flaggermusmannen; The Bat Man if literally translated), which is probably not something many brown people do on the way from Leicester to Birmingham.
The first two probably work best when heard rather than read, but they're still good fun to try out on others even if they don't quite work in print as you read them.
The third one's a real doozy. It took me the best part of the 50-minute train journey to work out. It's apparently quite a famous logic puzzle but I hadn't come across it before.
The answers are at the bottom of the post. Don't cheat!
1. Which single letter can you add to the beginning of the letters E, N, Y to make a word (in English)?
2. Which of the following is correct?
The yolk of an egg is white; The yolk of an egg are white
3. You wake up trapped in a room with two doors. One door leads to certain death and the other leads to freedom, but you have no idea which is which. There are two guards standing by the doors. They will let you choose one door but once you've made your choice there's no going back and you must walk through the door. You can ask one of the guards one question to help you make your choice. However, one guard always tells the truth, the other always lies and you don't know which is which. What is your question and which guard do you ask?
1. The answer is 'D' to make 'deny'. Most people cycle through the alphabet and miss the answer because they would say 'deni' in their heads and, quite rightly, decide that it isn't a word. According to the old chap on the train, native speakers of English are more likely to make this mistake than non-native speakers and variations of this task were used to catch spies out during the war.
2. They're both wrong. Egg yolks are yellow, not white. The mistake is to get hung up on the grammar of 'is' and 'are'.
3. This one's super tricky because it's not just which question you ask but what you do afterwards that also matters. The question should be something along the lines of 'If I want freedom, which door will the other guard say I should go through?' It doesn't matter which guard you ask, the important thing is to go through the opposite door to the one you're told.
Think about it for a minute.
If you ask the honest guard, he will honestly tell you that the other guard will lie and point to the door that leads to death. If you ask the lying guard, he will lie and tell you the honest guard will point to the door that leads to death. Which ever guard you ask and whatever the answer, the important thing is to go through the other door.