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

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

What Word am I Looking For ?

A landlord calls both of his sons and tells them that their horses will now decide who will transfer the inheritance. He tells them to race along the land till the end and the one whose horse will be slower will win and be the heir to all the property.

Both of them keep wandering for days but to no result. Then they ask a wise man regarding it. The man advises them on the matter after which they jump on the horses and race as fast as they can till the end. Why did they do it?

What did the wise man say?

You have a roll of cloth 1km long. You have a machine which cuts this roll into pieces of 10-meter-long cloth.

How long would it take for the machine to cut the roll if each cut took 4 secs?

We are a group of eight brothers. We consider the weak, yet we protect the king in every battle. If we move ahead, we never turn back. Who are we?

Be active and find the killer in the picture Riddle below.

See the given image carefully. What you have to do is move the blue checkers in the position of the black checkers and vice versa. You are only allowed to move the checker to an adjacent empty space. Do it in the least possible moves.

Replace the question mark with the number below given a simple math problem.

What is the relationship between these matchstick pictures below?

What 4-letter word can be written forward, backward or upside down, and can still be read from left to right?