What does this rebus means ?

PROG WORKRESS

A number can be multiplied by multiple of nine
i.e 9 18 27 36 45 ...

and the resulting number consist of only one digit.

Can you identify the number ?

You are given four tennis balls and asked to arrange those balls in a manner that the distance between each one of them is exactly equal. How will you do it?

It is always ahead of me yet I can never see it. What is it?

There is a shop where written:
Buy 1 for $1
10 for $2
100 for $3
I needed 999 and still only paid $3. How could this be financially viable for the shop-keeper?

There was a minor accident with a doctor's son but the doctor noticed no major injury. After the treatment, the father of that doctors son is sitting with the son of the doctor without the doctor being in the room.

How can this be possible?

Can you place three balls such that the equation shown in the picture holds true?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

Can you find out the remainder when 3^300 is divided by 5?

What jumps when it walks and sits when it stands?