What goes up but never comes down?

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

There are hundred red gems and hundred blue gems. The blue gems are priceless while the red gems equal wastage. You have two sacks one labeled Heads and the other Tails. You have to distribute the gems as you want in the two sacks. Then a coin will be flipped and you will be asked to pick up a gem randomly from the corresponding sacks.

How will you distribute the gems between the sacks so that the odds of picking a Blue gem are maximum?

If,
9 * 8 * 7 = 65
8 * 7 * 6 = 50
7 * 6 * 5 = 37

Find
6 * 5 * 4 = ?

Find The Missing Number In the Sequence.
6 25 64 ? 32 1

I don't get anymore wetter, no matter how much rain falls on me.

A 52% bias toss for head using the 51% tail bias coin was done to obtain a fair result.

Can you find how bias is the floor in this case?

When monkey rotate the gear, which mark will be hit 1 or 2 ?

Can it be possible to build a house that has all its four walls facing towards the South?

You need to arrange three 7 and mathematical symbols to form number 1?