You have two buckets. One holds exactly five gallons and the other three gallons. How can you measure exactly four gallons of water into the five gallon bucket?
Assume you have an unlimited supply of water and that there are no measurement markings of any kind on the buckets.
I am word with six letters. My motto is together as one. If you remove my first and second letters, you can wear me. If you remove my third letter I can be painful. If you remove my second, third and sixth letters, Adam & Eve did it. If you remove my second and third letters, you do this using your mouth. What am I?
String. A string ties objects together. You wear a ring, a sting hurts, according to the Bible, Adam & Eve committed a sin and you sing with your mouth.
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 give you a group of three. One is sitting down, and will never get up. The second eats as much as is given to him, yet is always hungry. The third goes away and never returns.