An infinite number of mathematicians are standing behind a bar. The first asks the barman for half a pint of beer, the second for a quarter pint, the third an eighth, and so on. How many pints of beer will the barman need to fulfill all mathematicians' wishes?

What breaks yet never falls, and what falls yet never breaks?

You can see three almost identical images below. Can you spot the odd one out from them?

By including only four matchsticks in below picture, you have to make "Four Triangles And Two Squares"

The more you take me, the more you leave me behind.
Who Am I?

Two guards were on duty outside a barracks. One faced up the road to watch for anyone approaching from the North. The other looked down the road to see if anyone approached from the South. Suddenly one of them said to the other, "Why are you smiling?"

How did he know his companion was smiling?

Solve the following series:
AZ, GT, MN, __, YB

What numbers should go on the bottom line?
3 6 9 15
8 2 10 12
11 8 19 27
19 10 29 39
? ? ? ?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

Three ants are sitting at the three corners of an equilateral triangle. Each ant starts randomly picks a direction and starts to move along the edge of the triangle. What is the probability that none of the ants collide?