What number when divided in half becomes zero?

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?

On a bright sunny day, two fathers took their son fishing in the lake. Each man and son were able to catch one fish. When they returned to their camp, there were only three fishes in the basket. What happened?

PS: None of the fish were eaten, lost, or thrown back.

There is a square of a particular number which when doubled, becomes 7 more than its quarter.

Can you find the number?

Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

You are stuck on an island where you have nothing. You find four pieces of paper somewhere on the island. What will be your strategy to escape from the island safely?

PS: No other resource is available to you on the island, neither can you build anything.

There is one thing that goes round the house and also inside the house but never even share a brief touch. What is it?

Look at the picture and find out which square is not linked with any of the other squares.