The letter X. It is the 24th letter of the alphabet, two Xs in Roman numerals equals twenty and triple x represents adult content, and adulthood is eighteen by law in most countries.
A variation of this brain teaser includes laser printers (they were invented by Gary Starkweather) and bulletproof vests (invented by Casimir Zeglen using silk, though modern vests use Kevlar, so it’s halfway right).
I stretch as far as a football field, Yet I fit in the palm of your hand. I will make you bleed if you don’t use me often. You put me in your mouth but don’t eat me, Then you throw me away.
Floss. It typically comes in 100 yard packs, which fit easily in your hand. If you don’t floss regularly, your gums will bleed. You use floss in your mouth then throw it away when you’re done.
A wise king devised a contest to see who would receive the Princess’ hand in marriage. The Princess was put in a 50 x 50 foot carpeted room. Each of her four suitors were put in one corner of the room with a small box to stand on. The first one to touch the Princess’ hand would be the winner and become the new King.
The rules were the contestants could not walk over the carpet, cross the plane of the carpet, or hang from anything; nor could they use anything but their body and wits (i.e. no magic, telepathy, nor any items such as ladders, block and tackles etc). One suitor figured out a way and married the Princess and became the new King. What did he do?
I am, in truth, a yellow fork From tables in the sky By inadvertent fingers dropped The awful cutlery. Of mansions never quite disclosed And never quite concealed The apparatus of the dark To ignorance revealed.
Four cards are placed in front of you on the table, each with a number on one side and a color on the other. The visible cards show 3, 8, red and brown. Which cards should you turn over in order to test the truth of the statement that if a card shows an even number on one face, then its opposite face is red?
You’d need to turn over only the 8 and brown card. Only a card with an even number on one face and which is not red on the other face can invalidate the stated rule. If you turn over the 3 card and it’s not red, it doesn’t invalidate the rule, nor does turning over the red card and finding it has the label 3.
This test was devised by Peter Cathcart Wason and is known as the Wason selection task. Less than 10% of test subjects got it correct in two separate studies.
