What does this mathematical rebus means ?

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?

What does this Rebus Picture means ?

What makes this number unique: 8,549,176,320?

A woman lives in a Tall building thirty-six floors high and served by several elevators which stop at each floor going up and down. Each morning she leaves her apartment and goes to one of the elevators. Whichever one she takes is three times more likely to be going up than down. Why?

What is the value of 1/2 of 2/3 of 3/4 of 4/5 of 5/6 of 6/7 of 7/8 of 8/9 of 9/10 of 1000?

Why is it very easy to weigh a fish?

You are a prisoner sentenced to death. The Emperor offers you a chance to live by playing a simple game. He gives you 50 black marbles, 50 white marbles, and 2 empty bowls. He then says, 'Divide these 100 marbles into these 2 bowls. You can divide them any way you like as long as you use all the marbles. Then I will blindfold you and mix the bowls around. You then can choose one bowl and remove ONE marble. If the marble is WHITE you will live, but if the marble is BLACK... you will die.'

How do you divide the marbles up so that you have the greatest probability of choosing a WHITE marble?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

The day after tomorrow will be three days before Tuesday. Can you find out what is today?