What runs around the whole yard without moving?

Find the next number in the series

12, 20, 40, 72, 116, 172 ?

What does this rebus riddle mean?

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?

He digs out tiny caves and stores gold and silver in them. He also built bridges of silver and made crowns of gold. They are the smallest you could imagine. Sooner or later everybody needs his help, yet many people are afraid to let him help them. Who is he?

A woman is sitting in her hotel room and hears a knock at the door. She opens the door to see a man whom she’s never met before. He says, “I’m sorry, I have made a mistake, I thought this was my room.” He then goes down the corridor and into the elevator. The woman goes back into her room and calls security. What made the woman so suspicious of the man?

I am dry when I go inside, but wet when I am pulled outside.
The longer I am inside, the stronger I get
When I am completely out, I am wet and I literally sag
Who am I?

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?

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

Can you find out a way through which you can make five squares out of the given figure by moving just six match sticks?