How can you make number one disappear by adding something to it?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

The below given figure comprises of a pattern through which you can determine the missing letter. Can you push your mind to find the pattern and add the missing letter?

A man wants to cross the pit of fire which is 25 feet in length and he has 2 planks(fire resistant) 19 feet in length. How can he cross the pit of fire alive?

Move three sticks of the spiral below to form a square.

You measure my life in hours
I serve you by expiring
I vanish faster when I am thin
and slower when I am thick
The wind is my energy
What am I?

Sherlock Holmes was challenged to make a pre-drawn line smaller without erasing it. He did it in fractions of seconds. How?

There is something which you can be arrested for attempting but not for successfully completing.

Which is the correct shadow of the bird?

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