Puzzles

.1. Quick Thinking If A is first, B is second, C is third etc., which is the only letter whose numerical order value begins with the same letter it refers to?
.2. Optical Illusion Here's a difficult one to work out. By re-arranging the four segments on the left to form the shape on the right, we gain a square.
.3. Optical Illusion The letters of the word LIFE appear to be tilting backwards and forwards. They're not, of course.
.4. Optical Illusion - Persistent Motion	By allowing your eyes to roam casually over the image, it appears to ripple. The effect is even greater if you use the scrollbar to slowly move the image up and down the page. Incidentally, the green shapes are not circles.
.5. Optical Illusion You either get this one straight away or spend ages struggling with it. It's a picture, but of what?
.6. Optical Illusion - Persistent Motion In this image we get the effect of three "drums" rotating left and right. The white edge shading on the blue discs determines which way each drum appears to turn.
.7. Just a Question This came about because of a discussion with a colleague at work. Neither of us has come up with a wholly convincing explanation for it. If you drop a single grain of sand onto a hard surface you won't hear it. Throw a cupful of sand onto the same surface and it will be clearly audible. Yet each grain of sand is effectively silent as it lands. What is it that actually increases the volume?
.8. Word Maze It might be an idea to print this one. Starting from the bold letter F in the grid you have to trace a sequence of words (of 4 letters or more) to take you back to the same letter. RULES: 1 No two consecutive words run in the same direction, and all words run in a straight line left, right, up, down or diagonally. 2 The last letter of each word serves as the first letter of the next word. 3 There are no plurals or capital nouns. 4 To correctively solve this puzzle you must trace a path of EXACTLY 12 WORDS - NO MORE, NO LESS!
.9. Pens For Pigs Not all farmyard animals are socially accomplished, and some even hate each other. So it is with farmer Jack's pigs. He has 12 of them, and there aren't two that can get on with each other, so they all have to be kept separately. Until now that hasn't been a problem, but last night there was a terrific storm that ruined the sties - he has some quick thinking and repair work to do before porcine attitude turns to all-out conflict. Sadly the storm damaged a lot of building material. All he has are 10 full length fences and 6 half length. How can he arrange them so that each pig can be housed individually? Don't think about cutting fences in half - they're much too expensive to start damaging them and, in any case, Jack will find an answer that keeps every piece of fencing intact.
.10. Absolutely Trivial Which is the only English League soccer club whose name can't be coloured in? Halifax Town, for example, isn't the answer because one can colour in the "O" of TOWN and part of either "A" in HALIFAX. The solution is unique regardless of whether you spell the name in upper or lower case.
.11. Which Switch? On the wall in front of me are three switches. Each is connected to one of three light bulbs in a room beyond. I can't see into the room - if I switch a light on there is no way I can know which one it is. I can only find out by entering the room and, for reasons unknown, there is a rule saying I can only enter once. How can I find out which switch is connected to which light bulb?
.12. Oops A nice photograph, except that it contains a fundamental error. Can you spot it?
.13. Where's the Square? Another re-arrangement of shapes as in #2, except this time the components are used to create the same triangle. Except - we've lost a square! How could that happen?
.14. Optical Illusion - Stop Spinning! Thirteen spinning discs and an example of very persistent motion. To stop the effect look at the centre of the pattern.
.15. Optical Illusion Incredibly, the two arrowed squares are identical in colour. Save the image to disk and open it in imaging software such as PhotoShop or PaintShop Pro. Each of these has a colour picking tool that will show you RGB values, so you can click the arrowed squares to confirm they really are the same.
.16. Human Body Trivia What is it that a human being can do until the age of around 6 months - after which point they'll never be able to do it again?
.17. Fun With Words I'm thinking of a 7-letter word containing three consonants and four vowels. The last letter is a consonant. By changing it to the next letter of the alphabet I create a new word (the order of the letters stays the same) - but, in the process, the pronunciation of every vowel in the original word changes. What are the two words?
.18. In Sequence What is the next number in this series? 7,8,5,5,3,4,4,6,9,_
.19. Optical Illusion Here we have what appears to be a dome of rock and/or earth. It looks like it's probably quite big - in fact, you wonder if the small dark dot in the middle may be a building, and there's the suggestion of a winding track nearby. Whatever they are, we've certainly been fooled into the accepting the dome idea. Place your cursor over the picture to turn it upside down and reveal the truth.
.20. Dead Simple It should be anyway. There's a new game in town - DOMINO CHESS. As its name suggests, the game makes use of a chessboard, a set of dominoes - and two coins. Each domino covers exactly two squares of the board; each coin covers one square. Player 1 places both coins on the board. He can place them anywhere but not adjacent to each other (this means they can't be arranged in a corner in such a way that a corner square is enclosed). For the sake of argument, let's say the two coins must be at least 3 squares apart. Player 2 must now use the dominoes to completely cover the rest of the board. If it's your turn to place the two coins, how can you guarantee that your opponent will be unable to cover the remainder of the board with the dominoes?
.21. Try This... Sit in a chair and lift your right foot a few inches from the floor, then begin to move your lower leg so that your foot is moving in a clockwise direction. While you're doing this, use a finger of your right hand to draw a number 6 in the air. Your foot will turn in an anticlockwise direction and there's nothing you can do about it!
.22. ...Or This Take a piece of uncooked spaghetti - you know, the dried stuff. Hold it between one finger of each hand then move the fingers together so that the piece of spaghetti breaks. It will break into 3 pieces or more, but never into just 2 pieces. Go on, try it.
.23. Cool Trick This is a great little trick. It's possibly more suited to a young audience, but it works with adults too - you just have to remember that it's a trick you can only perform once in front of your chosen audience - you'll see why when the method is explained. The effect: A member of your audience is presented with 3 pieces of card, each a different colour, from a sealed envelope that's been cut in half. You ask them to mentally choose one card - they mustn't tell you which one. After reading their mind, you ask them to point to the card they chose. You now reveal, in print, that you knew which card they were going to choose. The method: It's so simple! Let's imagine the pieces of card are BLUE, RED and GREEN. Inside the envelope, unseen as you do the trick, is another piece of card on which you have printed "You will choose the BLUE card". On the back of the envelope, also unseen, you have printed "You will choose the RED card" On the reverse of the GREEN card you have printed "You will choose this card". All you then have to do is remember which colour is associated with which printed statement.
.24. Dart Sharp! The challenge here is to score exactly 100 points. The illustration shows three darts - but you can use as many darts as you want.
.25. Split This Using only the grid lines, how would you split the square into two pieces so that they can be made into the rectangle?
.26. Four Queens - One Headache As you can see, this isn't a traditional chess board - it only has 7 x 7 squares. Fortunately, we're not playing chess. All you have to do is place four queens on the board so that: 1) Every remaining square is under threat from at least one queen, i.e. in the same vertical, horizontal or diagonal line. 2) None of the queens is under threat from another queen, i.e. in the same vertical, horizontal or diagonal line.
.27. INTERCHANGEABILITY Bearing in mind the puzzle title, which of the following is the odd-one-out? 3, 8, 9, 10, 13, 30, 38, 39, 80, 89, 90, 98
.28. ROT 13 ROT 13 is a popular alphabetical code in which the first half of the alphabet (A-M) is placed after the second half (N-Z), so A = N, B = O etc. Interestingly, the word NOWHERE thus becomes ABJURER, but here's one to ponder over; There is a 3-letter word which, when coded using ROT 13, forms a word which is synonymous with the original. What is it?
.29. Pointless Trivia... ...but interesting all the same. The popular image of a pirate - Long John Silver et al - sees him wearing an eye patch. It is easy assume that this is because of a noted historical pirate who wore one, and his fame/notoriety was such that the image came to represent pirates generally. There is a less "glamorous" - but possibly more interesting - reason.
.30. Odd-Man-Out The following list of words can be grouped into logical pairs, leaving one word on its own. What is the word - and what word would it need to form a pair? Incidentally, there is a reason for the use of two text colours. HINTS: One pair of words appears together. Also, in forming two of the pairs you have to start again at the beginning. CHAIN MILLS LORRY SUING BOURG MUNCH MOCHA INGOT CUSHY WOMBS SORRY VIOLA SATIN
.31. The Anagrammable Number 142857 looks like an unremarkable number, but the results are interesting when you multiply it by 2, 3, 4, 5 and 6: 142857 x 2 = 285714 \| 142857 x 3 = 428571 \| 142857 x 4 = 571428 \| 142857 x 5 = 714285 \| 142857 x 6 = 857142 In each case the result is the same sequence of numbers but starting from a different digit. Interestingly the start point (e.g., the 1) doesn't follow a pattern from product to product. And if you multiply 142857 by 7, by the way, you get 999999.
.32. 7-11 This is, as many of you will know, the name of a popular US store. This puzzle concerns a customer who enters such a store and buys four items. At the checkout, the cashier announces the total for the items is $7.11 - a nice coincidence, given the store's name. Out of curiosity, the customer asks how the figure was arrived at and is rather surprised when the cashier says "Oh, I just multiplied the costs of the individual items". "MULTIPLIED?" says the shocked customer. "Surely you mean ADDED?" "You're right" admits the cashier "but in this case the total would be the same". How much did each of the four items cost?
.33. The Unexplained Mathematical Loop This trick will probably require use of a calculator, if only for the sake of speed. What is impressive about it is that the loop we end up in has never been explained mathematically. Here's what you do: Select any 4-digit number in which there are at least 2 different digits (e.g. 4474 is OK but not 4444). Arrange the digits in increasing order and also in decreasing order (e.g. chosen number 3395 arranged as 3359 and 9533). Subtract the smaller number from the larger one. Re-arrange the digits of this answer as before - increasing and decreasing order - and again subtract the smaller from the larger. Keep repeating these steps and see what happens. The SOLUTION link above shows an example.
.34. Calculator Definitely Needed! This one will take some time but the effect is spectacular. Be sure to read the instructions very carefully then try it out on friends. 1 Give someone a sheet of lined paper and ask them to number the first 25 lines (i.e. 1-25). 2 Ask them to write ANY whole number on the first line, and ANY different whole number on the next line. 3 Add these two numbers together and write the result on line 3. 4 Repeat this process, i.e. adding together the last two numbers that have been written down and writing the result on the next line, up to and including line 25. Now for the really spectacular part - which definitely needs a calculator. 5 Take ANY NUMBER from the last five on the list, and divide it by the number immediately above. Remember: We started with 2 totally random numbers, and the final step involves selecting any one of 5 final numbers. Follow the SOLUTION link to see the answer - write it down on a piece of paper and astound your friends!
.35. The Written Number 1 What is the SMALLEST number which, when written, contains all five vowels? 2 What is the LARGEST number which, when written, does NOT contain the letter "N"? 3 How many numbers, when written, contain only one distinct vowel (i.e. the same vowel can be repeated)? 4 How many numbers, when written, contain no repeated letters? 5 What is the only number which, when written, has its letters in alphabetical order?
.36. Out! One for cricket fans. There are 10 ways in which a batsman can be given out. What are they?
.37. Probably Not What You'd Expect A pretty simple riddle, this one, but with an answer which may surprise you. Try to imagine the answer without actually going through with the instructions: Take a single piece of paper, roughly square although that's not important. Fold it in half, then in half again at 90 degrees to the original fold. Now cut it in half (parallel to an edge, not diagonally). How many pieces of paper will you now have? It's easy to think you'd end up with either two or four pieces of paper, but the actual answer is three. Go on - get a piece of paper and some scissors and try it.
.38. Just a Quickie Can you think of an antonym to the word "if"?
.39. Great Card Trick Take a standard deck of 52 playing cards and ask a member of the audience to shuffle them. Place the deck face down, write down the name of a particular card, then deal 12 cards, face down, onto the table. Ask the volunteer to indicate 4 cards - move these to one side and place the remaining cards on the bottom of the deck. Turn over the four cards; for example, King, 3, 8 and 5 (court cards = 10, Ace = 1). To each card, you add cards from the top of the deck to bring the value up to ten - i.e., no cards added to the King, seven cards added to the 3, two cards to the 8 and five cards to the 5. The next stage is to add together the values of the four chosen cards - King, 3, 8 and 5 = 26. The volunteer now takes the deck and deals 26 cards from the top. The 26th card is the one you wrote down. Method: There's no need to go into detail about how it works. All that's required is that when you take back the original full deck after shuffling you sneak a glance at the bottom card - this is the one whose name you write down. The rest is essentially arithmetic.
.40. Goodbye Dots A great optical illusion. Keep your eyes focused on the space in the centre of the three dots and after a few seconds they will disappear - sometimes together, sometimes one by one. For this to work properly it's important to not stare hard at the centre - try to keep your vision as relaxed as possible.
.41. The World's Simplest Card Trick? This requires no preparation whatsoever but it can be incredibly effective. Best of all, it's a trick that can be accomplished without you laying a finger on the deck of cards. In fact, we'll describe it with that in mind. Give someone the deck of cards and ask them to think of TWO card values, without looking at the pack. Ignore suits - we just want numerical or rank values, for example a 6 and a Jack. Get them to tell you these two values. Now ask your subject to turn the cards over one at a time, face up onto the table, while you concentrate very hard on the pack. As if by magic, they will eventually turn over the 6 and the Jack together! Method: There is no method - it's all a matter of probability. On perhaps one occasion out of ten the two cards will be separated by one other, in which case you just claim you weren't concentrating hard enough.
.42. Optical Illusion There is no green ball! Keep your eye on the cross in the middle and you will be convinced that a green ball is circulating the perimeter of pink disks. You may also find that the pink disks disappear altogether. It's interesting to note that if you open this .gif image in a viewer that does not show the animation, then look at the black cross for a few moments, you'll see a ghost image of green disks when you let your eyes move away from the cross.
.43. Magic Sudoku The idea of a sudoku puzzle with just NINE starting numbers probably sounds ridiculous. In the normal course of events it is ridiculous. However, if you apply a few extra rules to the game you end up with something like this - a truly magnificent twist on sudoku's simple concept.
.44. Kakuro Puzzle Having downloaded the excellent Kakuro Epic software, we've seen what it can do and we're impressed! There's a 14x14 puzzle to try HERE.
.45. Dice To Ponder Just a little optical illusion offering which I've included merely because - while the principle is an old one - this is the first example I've seen of an impossibility shown as a photograph.
.46. Another Split-The-Shape Puzzle The illustration on the right is a 7x10 rectangle with an empty space in the middle, shown in yellow. Can you divide the shape into two equal segments so that they can be re-assembled to form a 8x8 square?
.47. Rubik's Cube Optical Illusion Of interest to us in this illusion are only the central pieces of each of the three visible sides. Two sides are lit and have a brown tile in the middle. The side in shadow has a yellow tile in the middle. Or does it? Use the colour picker in any imaging software and you'll find all three central tiles are exactly the same colour.