How many triangles are there on the puzzle below?

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

My friends called me Iron59 because my parents are a chemist and a mathematician. What is my real name?

In an interview, a boy was asked an unusual question 'How two persons sitting with a table in between them can't see each other?' He was unable to reply. Can you?

If you toss a coin 10 times and it lands heads up every time, what are the chances it will land heads up if you toss it again?

You are given with the following sum. Each of the letters can be decoded as a digit. If we tell you that D = 5, then can you solve it entirely?

DONALD
+GERALD
=ROBERT

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?

How can you take 2 from 5 and leave 4?

What does the following represent?

N N N N N N N

A A A A A A A

C C C C C C C