How many people must be gathered together in a room, before you can be certain that there is a greater than 50/50 chance that at least two of them have the same birthday?

What has many keys but can’t open a single lock?

Can you solve the tricky chess rebus puzzle below by ciphering the hidden meaning?

what one word does the below rebus identifies?

Count the number of triangles in the picture below:

A bomb exploded in a room full of married couples and no one died. How?

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

Your last good ping-pong ball fell into a narrow metal pipe embedded one foot deep in concrete.
How can you get it out undamaged, if all the tools you have are your tennis paddle, shoe laces, and plastic water bottle, which does not fit into the pipe?

What is black when you buy it, red when you use it, and gray when you throw it away?

Can you convert the number zero(0) into a positive number using just one mathematical operator ?