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

What Word am I Looking For ?

Before Mount Everest was discovered, what was the highest mountain in the world?

I went to the bookshop and spent one-half of the money that was in my purse.

When I came out, I found that I had as many cents as I had dollars and half as many dollars as I had cents when I went in. Find the money in my purse when I entered the store.

A lion and its tamer are standing inside a cage that measures 1 unit in radius. Both of them can effortlessly run at the speed of 1 unit maximum.

1) Suppose the lion is hungry, will he be able to eat up the tamer?
2) If yes, how long can the tamer survive?

Can you decipher the two rows to find the hidden word?

The following alphametic has only one solution. Can you find it?
ENLIST + SILENT + LISTEN = ANAGRAM

PS: You may start the number from 0.

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

Move four matchsticks to the below square to form three squares?

Solve this riddle by finding the odd one out from the rest.

Why did Buffon take the goal with him after every Juventus match?