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.
You watch a group of words going to a party. A word either enters through one of two doors or is turned away by the guards. ‘HIM’ goes through door number one and ‘BUG’ goes through door number two. ‘HER’ is turned away. ‘MINT’ and ‘WEAVE’ go in through door one, ‘DOOR’ and ‘CORD’ take door two and ‘THIS’ and ‘That’ aren’t allowed in.
What determines whether a word can enter and which door they must use?
Door number one is for words composed entirely of capital letters written using only straight lines, such as A, E, F, H, and I. The entire set of letters allowed through door number one are AEFHIKLMNTVWXYZ. Door number two, as might be expected, is for words with capital letters that have a curve, including BCDGJOPQRSU. Any words composed of both straight and curved letters (or lowercase letters) are not allowed in. The word ‘THAT’ would have been sent through door number one, if the letters had been capitalized.