What is the coolest letter in the alphabet?

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 the Chess Board picture below white army is arranged. You need to add a black army on the board such that no piece is under any threat.
Note: Army comprised of 1 king, 1 queen, 2 rooks, 2 bishops, 2 knights, and 8 pawns.

Can you count the number of triangles in the given picture?

Can you find the missing piece of the Porsche?

You have three orange, two pink and five purple balls in the drawer beside your bed. There is no electricity and the room is entirely dark. How many balls must you take out to ensure at least one ball of each colour at least?

What jumps when it walks and sits when it stands?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

This puzzle is for Harry Potter fans. Do you know why Tom Riddle is called Lord Voldemort?

What is more useful when it is broken?