What goes up but never comes down?

What have one eye but still cannot see?

An artist while painting a scenic beauty, decides to paint three layers of blue colour on the sky.

Which layer will go on the first?

Replace the question mark with the correct number, given the pair of numbers exhibits a similar relationship?

? : 3839 :: 11 : 1209

Trying to tease Birbal, Akbar gave him one gold coin and ask him to buy
* something for him to eat
* something for him to drink.
* something to feed the cows
* something to plant in the garden
and most important you need to buy only one thing.

What must Birbal buy to silence Akbar?

What happened when the wheel was invented?

You have three orange, two pink and five purple balls in the drawer beside your bed. There is no electricity and the room is entirely dark. How many balls must you take out to ensure at least one ball of each colour at least?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

What number does the below three word/phrase identify and why?
1. Deck
2. Year
3. Singing in the Rain