What has many keys but can’t open a single lock?

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?

Before Mount Everest was discovered, what was the highest mountain in the world?

Can you name any English verb that becomes its past tense by simply rearranging the alphabets ?

In an interview, a boy was asked an unusual question 'How two persons sitting with a table in between them can't see each other?' He was unable to reply. Can you?

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

How many times can you subtract the number two from the number fifty?

I make two people out of one. What am I?

If eleven plus two equals one, what does nine plus five equal?