What does an Island and the letter T have in common?

There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

13 decks of cards have been mixed. What is the minimum number of cards that must be taken out from the above-mixed cards to guarantee at least one 'four of a kind?

In which direction should the missing arrow point?

I am the fastest animal but cannot climb the tree. What am I?

Can you make numbers like 24, using numbers 3,3,7 & 7 with any arithmetic operator?

It belongs to you, but other people use it more than you do. What is it?

In a supermarket, there is an intelligent glass pane before a refrigerating unit. This glass pane allows cherries and apples through it but does not allow grapes and Orange to pass through it.

Can you identify the rule that the glass pane is following?

I come in different shapes and sizes.
Parts of me are curved, other parts are straight.
You can put me anywhere you like,
but there is only one right place for me.
What am I?

Two-person want to cross a river. Only one boat is present on the riverside that can carry only one person at a time.

However, they still manage to cross the river. How is it possible?