The more of this there is, the less you see. What is it?

As a whole I am both
safe and secure.

Behead me and I become
a place of meeting.

Behead me again and I am
the partner of ready.

Restore me, and I become
the domain of beasts.

What am I?

There are 2 sand hourglasses.

The small one can measure 5 hours and the large one can measure 7 hours.

How can we measure 16 hours with 2 sand hourglasses running together ?

Readers with the most attentive eyes can find three differences between the crocodile pictures in 10 seconds. Can you? Test your attentiveness now!

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.

How is a fly different from a mosquito?

Find The Missing Number In the Sequence.
6 25 64 ? 32 1

A man says, "Brothers and sisters, have I none, but that man's father is my father's son." Who is that man?

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

What is the next number?

77, 49, 36, 18 ?