Thanks to www.syvum.com for this brain teaser:
A 33″ x 33″ square metal plate needs to be fixed by a carpenter on to a wooden board. The carpenter uses nails all along the edges of the square such that there are 34 nails on each side of the square. Each nail is at the same distance from the neighboring nails. How many nails does the carpenter use?
Answer will follow in the comments section below in 1-2 days.