Loophole Abuse in puzzles.
- A puzzle requires drawing a full box with an X in the middle without taking your pencil off the paper. Normally, this would be impossible...but there Ain't No Rule that says you can't fold the paper over before you start to draw; with this trick, you just draw a square "C" over where the paper overlaps, unfold the paper so the "c" "breaks" into two horizontal lines, then draw an hourglass in the empty space, all without lifting up the pencil. A Variant: draw a circle with a dot in the middle without taking your pencil off the paper.
- Since the exact dimensions the x in the middle of the box must be aren't specified, you can also get away with this one: Draw one side of a square and then draw a diagonal line, which will connect to the other end of the opposite side of the square, which you then draw. Repeat this on the other side to finish the x, and then complete the box by drawing the final two sides of the square, tracing over previously drawn lines to avoid having to lift your pencil.
- In that case, you take a pencil, place it on a piece of paper, then casually whip out a pen with which you then draw the dotted circle... Without the pencil leaving the paper.
- Alternately, use a mechanical pencil, draw a circle, press on the button to retract the lead, move to the center of the circle, press the button again to extend the lead, and complete the dot. That puzzle also makes no mention regarding overlapping lines, meaning you can draw the box, draw a diagonal from the last corner, retrace a side, then do the other diagonal.
- With a wooden pencil, draw the dot, then lower the pencil onto its side, slide it along the paper until you get to where the circle would be and tilt it back up to draw the circle. The rules do not specify that the point of the pencil has to be in contact with the paper.
- It's not uncommon to encounter a number puzzle that has no solution unless you exploit the rules in this fashion. For example, there's a famous Henry Dudeney puzzle where you have to circle six of the following numbers to make a total of 21: 9, 9, 9, 7, 7, 7, 5, 5, 5, 3, 3, 3, 1, 1, and 1. It can't be done as intended, because the total will always be even. Dudeney's solution? There Ain't No Rule saying you can't turn the paper upside-down first, letting you circle three 6s and three 1s. Then a reader came up with an alternative solution; drawing a single circle around two 1s to get 11, then circling three 3s and the other 1.
- The classic "nine dots" puzzle challenges you to connect a square of nine dots with just four straight lines without lifting your pen from the paper. It's impossible to do this unless you "think outside the box" and notice that there's nothing in the puzzle that forbids letting the lines run outside of the square.
- Or you can fold the paper, use a very thick line, connect your four straight lines with a few curvy lines, etc.
- Nobody said what shape it had to be, you can start at one corner, go out, go diagonal, go back, and go diagonal again.
- Use a pencil.
- Use a pen that isn't yours.
- Roll paper into a cylinder, then draw spiral line around paper that touches all 9 dots.
- Tie a knot in a length of rope with both hands without letting go of the rope. There Ain't No Rule saying you can't tie your arms in a knot first (i.e., fold your arms).
- Or tie the knot around your arm, or tie an unknot
, or stop holding it with one hand, but keep a firm grip with the other, and thus not letting go, or tying the knot in a different part of the rope, or don't hold on with your hands in the first place (but still use your hands in some other way) or hold the rope in a circle around you while tying a knot with a piece of string while inside the circle.
- Or tie the knot around your arm, or tie an unknot
- Most assume that the answer to the old brainteaser "Who is buried in Grant's tomb?" is Ulysses S. Grant, but the true answer is "nobody". While Grant and his wife are interred in his tomb, they are interred in above-ground sarcophagi. Thus, nobody is truly "buried in Grant's tomb".
- The question was used on You Bet Your Life as one of the $25 consolation questions given to contestants who didn't win anything. True to the popular assumption, "Grant" was the accepted answer; when a contestant gave the true answer, Groucho Marx was shocked that he managed to get the question "wrong", forcing him to point out the "above-ground sarcophagi" technicality.
- One worksheet that is sometimes given to students in (usually elementary) school describes the classic "You are in a supermarket but find that your cart can only make left turns. Navigate the supermarket, getting everything on your list making only left turns"-maze scenario. The intended solution involves making three left turns for every right turn you would make normally, but there's no rule stating people can't draw a U-turn back to the start (where they get the cart) and write, "Get a new cart that isn't broken."
- Joke chess problems, including one that involved castling vertically with a promoted rook, and another that requires promoting a pawn to a knight of the other colour. Both problems prompted Obvious Rule Patches in the rules of chess; the color-switching promotion is not legal anymore, and after the vertical castling puzzle was published, FIDE clarified that castling had to be done on the same rank as the King (these rules had been followed as long as modern chess had been around; but the loophole was finally closed).
- At one point, the rules said "The King is in check when the square on which it is standing is attacked by one or two enemy pieces." This was under the assumption that players would "play normally", since it's only possible to uncover two attacks on the same piece in any one turn. However, one composer noted that this meant that a player could get out of a double-check by getting a third piece to attack the king (e.g. by moving a piece off the line of attack of said third piece, revealing the king behind it)...
- It's a common convention in chess problems that castling is always legal, except where it can be proven otherwise. So composer Armand Lapierre constructed a chess problem where White's castling rights can't be disproven, but White and Black can't both have castling rights. The solution is therefore for White to castle (this is possible since it can't be disproven), which therefore makes Black unable to castle, allowing White to checkmate Black on the next move! This and similar problems drew criticism from the chess problem community for the "non-chess" motivations behind White's first move.
- A commonly accepted answer to the St Ives riddle (I met a man with seven wives, every wife had seven sacks, every sack had seven cats, every cat had seven kits) is “One”. This assumes that the men, wives, sacks, cats and kits are coming away from St Ives and only the speaker is going TO St Ives. The question itself doesn’t specify this and you’re most likely intended to actually do the math. Or one can interpret the phrase "Kits, cats, sacks, wives, how many were going to St Ives?" to mean how many of the kits, cats, sacks and wives were going to St Ives, in which case the answer is zero. (It is never specified that the man actually brought his wives et al. along with him.)
- Once upon a time, a wealthy Arabic man with two sons died. The will said that, to inherit the fortune, the sons would have to participate in a camel race. The heir would be the owner of the slower camel. Dumbfounded, the sons pondered for a while how to do this without the race taking forever. They ended up asking a wise old man for advice. What did the man say? Simple: the sons just needed to borrow one another's camels, then run for the destination as fast as possible. If the elder son arrived first, that meant the faster camel was that of the younger son, which made the elder's camel the slower one, and therefore the elder would inherit. Conversely, if the younger son arrived first, that meant his own camel was the slower one, so he would inherit the fortune.
