How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9?

What will you call your mother's brother's brother-in-law?

Can you complete the sequence?

192, 021, 222, 324, 252, 627, 2__, 9__?

In the image below, you can see two glasses and two matchsticks.You need to move four matchsticks in such a manner that the crosses come inside the glasses. Note: you cannot move the crossed.

What does the following represent?

N N N N N N N

A A A A A A A

C C C C C C C

Find the next number in the series

12, 20, 40, 72, 116, 172 ?

A chess tournament is taking place on knock-out terms (the one who loses the match is out of the game).
(a) If 10 matches are played in total, how many players participated?
(b) If 20 players took part in the tournament, how many matches were played?

The host of a game show, offers the guest a choice of three doors. Behind one is a expensive car, but behind the other two are goats.
After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter?

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.