When I get multiplied by any number, the sum of the figures in the product is always me. What am I?

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

What have one eye but still cannot see?

I’m light as a feather, yet the strongest person can’t hold me for five minutes. What am I?

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?

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?

I’m orange, I wear a green hat and I sound like a parrot. What am I?

Can you find the missing piece of the Porsche?

Twenty frogs are sitting on a log floating on the surface of a river. Two of them decide to jump off into the water.

How many frogs are there on the log at this moment?

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?