What goes up but never comes down?

I have some blue and red sock in my drawer. I have a total of 4 socks. I pick 2 socks and the chance that I get a pair of red socks is 1/2.

What is the chance of picking a pair of blue socks?

Railroad Crossing, look out for the cars. Can you spell that, without any R's ?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

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?

Remove two matchsticks to make the below equation correct.

Why 1729 is a magic number? Answer Logically.

In a chess board, the queen piece can move horizontally, vertically and diagonally freely. The picture represents the same.Can you place 8 queens on the board in a manner that none of the queens can attack each other?

Can you find the six hidden animals in the picture below?