Which country gets ill every time?

Find The Next Number in this series.
1, 2, 6, 42, 1806 ?

Count the number of balls in picture below:

I am quite hot but become too cold if you remove the first two letters. What am I?

Can you find the missing number in the third row?
35 20 14
27 12 18
5 2 ?

How many Watermelons are there in the below picture?

Which is the smallest number that you can write using all the vowels exactly once?

Find out a multi-digit number that if multiplied by the number 9 or any of its multiplications products (i.e. 18, 27, 36, 45,..) will result in the multiplication factor repeated (n) number of times.

What three numbers, none of which is zero, give the same result whether they’re added or multiplied?

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?