Why are all black people so quick ?

Can you find a five letter word that is left with only two letters if one is removed?

I have a mouth but I don't eat.
I have a bank but have no money.
I have a bed but i dont sleep.
I wave but have no hands.

Who Am I ?

I am a word of 12 alphabets.

* Alphabets 12, 4, 7, 2, 5 : Eastern beast of burden
* Alphabets 1, 8, 10, 9 are street made famous by Sinclair Lewis.
* Alphabets 11, 3, 6 are past.

On whole it means a person suffering from delusions of greatness.

What Is it ?

A King wants to send the diamond ring to his girlfriend securely. He got multiple locks and their corresponding keys. His girlfriend does not have any keys to these locks and if he sends the key without a lock, the key can be copied in the way. How can King send the ring to his girlfriend securely?

Buy me, smell me or deliver me, I do not change.

Who am I?

What is the four-digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?

A prisoner is told: "If you tell a lie, we will hang you and if you tell the truth, we will shoot you." What did the prisoner say to save himself?

Known by all without exception, Forever here, for your protection, Sometimes strong, sometimes weak, Right after the night I come - hot and chic. And while millions of miles away, I always get to you, I find my way. No life around could do without me, Can you guess what I might be?

Considering the below equation:

V + II - VI = 10
IV - X + VIII = 20
IV - VII + VI = 30

Then, I + II + III = ?