What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

You knock a Table over in the library, and suddenly 20 eyes are looking at you.

Can you count the number of triangles in the picture below?

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

How many people must be gathered together in a room, before you can be certain that there is a greater than 50/50 chance that at least two of them have the same birthday?

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?

How many sides does a circle have?

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?

Can you find out the remainder when 3^300 is divided by 5?

In a secret society, a buried chamber can be accessed only via a secret password. The password is seven characters long and comprises of just letters and numbers.

You find a code that can help you in cracking the password. The code says "You force heaven to be empty".

Can you deduce the password from that?