Can you place six X (crosses) in below board without making three in a row in any way ?

Can you find out which options fits best with the missing column?

Prove that twice of ten is the same as twice of eleven.

On one occasion, A Boy collects 71 rupees in form of 20 paise and 25 paise. He collects a total of 324 coins.

Can you tell me how many 20-paisa and 25-paisa he got?

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 breaks yet never falls, and what falls yet never breaks?

By moving exactly three matchsticks can you make the below equation true.It can be solved by 3 ways.

If 2 workers can complete painting 2 walls in exactly 2 hours.

How many workers would be needed to paint 18 walls in 6 hours?

How many triangles are there in the picture below?

No matter how little or how much you use me, you change me every month. What am I?