Why do people go to bed?

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

Find three numbers such that

* When we multiply three numbers, we will get the prime numbers.
* The difference between the second and the first number is equal to the third and second.

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.

In which direction should the missing arrow point?

In a science lab, a petri dish hosts a healthy colony of yeast for an experiment. Now every minute, all the yeast cells divide into two. At noon, there was just a single cell of yeast and at 1:22, the Petri dish was half full. Can you calculate when the dish will be full of yeast?

Complete the following series. It.s very logical:

1, 4, 5, 6, 7, 9, 11, __?

A maths symbol is hidden in the below Bar Graph. Can you decipher it?

All of the flowers I have are orchids except two. All of the flowers I have are hibiscuses except two. All of the flowers I have are roses except two.

Can you tell me how many flowers I have?

If 21x = 79x, what is the value of x?