Why is the Hole below a Lock?

What is the fastest way to double your money?

Replace the question mark with the number below given a simple math problem.

The owner of a popular clothing store comes up with his own method of pricing items. A vest costs $8, socks cost $10, a tie costs $6, and a blouse costs $12. Using the owner’s method, how much would a pair of underwear cost?

Three ants are going up a hill, one behind the other. The last ant then says to the other ants, 'There is an ant behind me!'' How come?

Luis Garavito killed Density x Volume.

Who is Luis Garavito ?

Can you find the 09 errors in the picture below?

Can you find out which triangle will have a bigger area among the following?
1. A triangle with sides 300, 400 and 500
2. A triangle with sides 300, 400 and 700

I am five letter word that is under you.
If you remove my 1st letter, then I am over you.
If you remove my 1st and 2nd letters then I am all around you.

Who am I?

I am the beginning of the end, and the end of time and space. I am essential to creation, and I surround every place. What am I?