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

Two friends were stuck in a cottage. They had nothing to do and thus they started playing cards. Suddenly the power went off and Friend 1 inverted the position of 15 cards in the normal deck of 52 cards and shuffled it. Now he asked Friend 2 to divide the cards into two piles (need not be equal) with equal number of cards facing up. The room was quite dark and Friend 2 could not see the cards. He thinks for a while and then divides the cards in two piles.

On checking, the count of cards facing up is same in both the piles. How could Friend 2 have done it ?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

What does this rebus means ?

PROG WORKRESS

In The 1st month of this year(the year 2013), I noticed that the date 13-1-13 (13 January 2013) is special.

This date is special as:

Date * Month = Year.

Can you figure out which year of this century has a maximum number of such dates?

A word I know,
Six letters contain,
Subtract just one,
And twelve is what remains.

What does below science rebus mean?

Ag Ag Ag
Ag SPOON Ag
Ag Ag Ag

It has horns but can’t beep. It is like to bleat but It is not a sheep. What is it?

What number do you get when you multiply all of the numbers on a telephone's number pad?

What do you think with the below Picture ?