Why do you find that most of the buildings are deprived of the 13th floor?

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

I don't get anymore wetter, no matter how much rain falls on me.

I am eight letters long - "12345678"
My 1234 is an atmospheric condition.
My 34567 supports a plant.
My 4567 is too appropriate.
My 45 is a friendly thank-you.
My 678 is a man's name.

What word am I?

A maths symbol is hidden in the below Bar Graph. Can you decipher it?

If 21x = 79x, what is the value of x?

One absent-minded ancient philosopher forgot to wind up his only clock in the house. He had no radio, TV, telephone, internet, or any other means for telling time. So he travelled on foot to his friend's place a few miles down the straight desert road. He stayed at his friend's house for the night and when he came back home, he knew how to set his clock. How did he know?

Find three whole, positive numbers that have the same answer when multiplied together as when added together.

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see? What is it?

A man is trapped in a room. The room has only two possible exits doors. Through the first door there is a room constructed from magnifying glass. The blazing hot sun instantly fries anything or anyone that enters. Through the second door there is a fire-breathing dragon. How does the man escape?