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

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

Which statement is true out of the following?
One statement here is false.
Two statements here are false.
Three statements here are false.

What has one letter and starts with an E?

ENEMY = 2 * LINK
LINK + 2 = HELL

Then what will be TAXI + HELL? Select from the options below:
a) ROTTEN
b) DANGER
c) HEAVEN
4) MORTAL

What can you hold in your right hand, but never in your left hand?

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

What Am I?

You are presented with three boxes. One of them has a red ball inside and the other two have a black ball inside each of them. You are asked to pick up the one with red ball and you pick one. Now, one of the other boxes is opened and it is found to have a black ball.

You are presented with a chance to change your box with the one that is left closed. Will you change your box? Why or why not?

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

The King of a distant land had heard that Birbal was one of the wisest men in the East and so desired to meet Birbal. He sent Birbal an invitation to visit his country.

In due course, Birbal arrived in the distant kingdom. When he entered the palace he was flabbergasted to find not one but six kings seated there. All looked alike. All were dressed in kingly robes. Who was the real king?

The very next moment he got his answer. Confidently, he approached the king and bowed to him.

How did Birbal know who was the real king?