Before Mount Everest was discovered, what was the highest mountain in the world?

Can you find out which options fits best with the missing column?

Can you count the number of triangles in the given figure?

Replace the question mark with the correct number in below Picture:

What is both possible and impossible 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.

It can't be seen, can't be felt, can't be heard, and can't be smelt.
It lies behind stars and under hills, And empty holes it fills.
It comes first and follows after, Ends life, and kills laughter.
What is it?

How can you leave a room with two legs and return with six legs?

What are the 50th, 63rd and 100th numbers in the sequence below?
4, 5, 8, 8, 9, 9, 12, 13, 13, 13, 17, 18, ...

What does below Rebus say?

XLR8