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

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 man died and leaves Rs.10,000 in his will. There are 6 beneficiaries- his 3 sons and their wives. The 3 wives receive Rs.3960 of which Priyanka gets Rs.100 more than Tanu and Neha gets Rs.100 more than Priyanka.
Pramod gets twice as much as his wife, Tushar gets the same as his wife, and Prashant gets 50% more than his wife.

Who is married to whom?

A girl is twice as old as her brother and half as old as her father. In 50 years, her brother will be half as old as his father. How old is the daughter now?

What is the Surname of Barbie Doll?

What word is pronounced the same if you take away four of its five letters?

On my way to St. Ives I saw a man with 7 wives. Each wife had 7 sacks. Each sack had 7 cats. Each cat had 7 kittens. Kittens, cats, sacks, wives. How many were going to St. Ives?

The product of three consecutive numbers is 7980.
Then the sum of these consecutive numbers would be?

My location can be determined by the below rebus.
So where am i ?

What number when divided in half becomes zero?