They came out at night, without being called.
They lost at day, without being stolen.
Who are they?

What number do you get when you multiply all of the numbers on a telephone's number pad?

How many letters are in the alphabet?

How many triangles can you find in this given picture?

If you go to the movies and you're paying, is it cheaper to take one friend to the movies twice, or two friends to the movies at the same time?

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.

A man dies of old age on his 25 birthday. How is this possible?

Can you solve this picture maths equation?

Accidentally, two trains are running in the opposite direction and enter a tunnel that is 200 miles long. A supersonic bird that has fled the lab and taken shelter in the tunnel starts flying from one train towards the other at a speed of 1000 mph. As soon as it reaches the second train, he starts flying back to avoid collision and meets the first train again at the other end. The bird keeps flying to and fro till the trains collide with each other.

What is the total distance that the supersonic bird has traveled till the trains collided?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?