There is one thing that goes round the house and also inside the house but never even share a brief touch. What is it?

What is the word or phrase?

I add 5 to 9 and get 2. The answer is correct, so what am I?

A non-stop marathon is the shared favourite sport of three brothers.

*The oldest one is fat and short and trudges slowly on.
*The middle brother's tall and slim and keeps a steady pace.
*The youngest runs just like the wind, speeding through the race.

"He is young in years, we let him run!" the other two brothers explained, "'because though he is surely number one, he is second, in a way." Why is it?

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

What brings you down but never up?

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?

Replace the question mark with the correct number in the below-given picture?

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.

I have a mouth but I don't eat.
I have a bank but have no money.
I have a bed but i dont sleep.
I wave but have no hands.

Who Am I ?