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

? : 3839 :: 11 : 1209

If you’ve got me, you want to share me; if you share me, you haven’t kept me. What am I?

Count the squares in the matchstick puzzle below?

I have a five and a three-gallon jar. Assuming there is an infinite supply of water, how can I measure one-gallon water?

How many triangles do you see in the picture puzzle below?

Can you solve the photo plexer logic ?

You need to move three matchsticks to form three squares. Can you do it?

Spot 5 differences in two Christmas tree below:

Three people enter a room and have a green or blue hat placed on their heads. They cannot see their own hat but can see the other hats.
The colour of each hat is purely random. They could all be green, blue, or any combination of green and blue.
They need to guess their own hat colour by writing it on a piece of paper, or they can write 'pass'.
They cannot communicate with each other in any way once the game starts. But they can have a strategy meeting before the game.
If at least one of them guesses correctly they win $10,000 each, but if anyone guesses incorrectly they all get nothing.
What is the best strategy?

What is wrong in the below Picture?