Can anyone tell me a word in the English dictionary which has a silent 'z'?

You have two strings whose only known property is that when you light one end of either string it takes exactly one hour to burn. The rate at which the strings will burn is completely random and each string is different. How do you measure 45 minutes?

Which is faster, Heat or Cold ? Explain.

John’s parents have three sons: Snap, Crackle, and what’s the name of the third son?

A man is trapped in a room. The room has only two possible exits doors. Through the first door there is a room constructed from magnifying glass. The blazing hot sun instantly fries anything or anyone that enters. Through the second door there is a fire-breathing dragon. How does the man escape?

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

What is so fragile that saying its name breaks it?

The centre of the third figure is empty. What digit should fit inside?

Replace the question mark with the number below given a simple math problem.

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.