What is the fastest way to double your money?

What is the next number in this series?

4,12,84,3612....

If it took eight men ten hours to build a wall, how long would it take four men to build it?

How can you write nineteen in a manner that if we take out one, it becomes twenty?

Lifeless eyes on my smiling face and watch your child's sleeping place. In their dreams they hold me tight. What am I?

Using Only Five 5's and any mathematical operator make sum as 37

Sachin bought a car with a strange 5 digit numbered plate.The water image of the number is 78633 more than my car number. All the digits of car number are distinct.

What is the original number on number plate?

What do you call a fish without an eye?

Identify Me

Hint1: I am a god
Hint 2: I am a planet
Hint 3: measurer of heat

What do you answer even though it never asks you questions?