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?

Here is a mathematical expression that also secretly tells a movie name. What movie is that?

Move three sticks of the spiral below to form a square.

What does this simple rebus mean?

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?

How many times can you subtract the number two from the number fifty?

What has hands, but can’t clap?

Can you find out the next digit in the following series ?

0, 0, 1, 3, 2, 6, 3, 9, 4, 12, 5, ?

How much will a 38° angle measure when looked at under a microscope that magnifies ten times?

Using the clues below, what four numbers am I thinking of?

The sum of all the numbers is 31.
One number is odd.
The highest number minus the lowest number is 7.
If you subtract the middle two numbers, it equals two.
There are no duplicate numbers.