What has hands, but can’t clap?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

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?

f you were running a race, and you passed the person in 2nd place, what place would you be in now?

Name a key which is hardest to turn.

The picture shows the dice results in each couple of throws. If they are actually following a pattern, can you find out the missing one?

Can you convert the number zero(0) into a positive number using just one mathematical operator ?

Can you find out the total number of triangles in the given figure?

I start and end with 500 and carry a 5 in my heart. But I require the first letter and the first number to be complete. I am the name of a King.

Who am I ?

I am a five-letter word and people eat me. If you remove the first letter I become an energy form. If you remove the first two letters, I am needed to live. Scramble the last three letters and I am a drink. What word am I?