Every Friday on my blog I present a puzzle, challenge people to try to solve it over the weekend, and then post the answer on the following Monday.  I avoid cryptic crosswords and number grids, and instead focus on the type of quirky puzzles that are likely to produce that rare but satisfying ‘a-ha’ moment.

The Friday Puzzle has attracted a large and loyal following, with people frequently arguing about the best way to tackle the various problems, and often coming up with new and ingenious answers.

Here are 101 of my favourite Friday Puzzles.  If you are stumped, or want to check your answers, I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here).

Puzzle 1 – Inside the dungeon

You are trapped in a dungeon with only a small amount of food and water.  The guard takes a piece of chalk from his pocket and draws the Roman numeral for 9 on the wall.  He then hands you the chalk and challenges you to draw one single continuous line and turn this into a 6.  If you can solve the puzzle then you get an extra helping of food.

Puzzle 2 – Time for an equation

Annoyed, the guard then draws the following equation on the wall…

IO  IO  II = IO.50

…and challenges you to add a single line to make it correct.  Oh, and there is just one rule – you are not allowed to place your line over the equals sign in order to convert it into a ‘not equals’ sign!  Can you solve the puzzle?

Puzzle 3 – The Race

You are a cyclist in a cross-country race. Just before getting to the finish line you overtake the person in second place.  What place did you finish in?

Puzzle 4 – Horsing around

Look at this picture of a horse.

Can you figure out why this picture is so riveting?

Puzzle 5 – Jason, my pet frog

My pet frog is called Jason. Jason has been a very silly frog and fallen into a well that is 12 feet deep.  Now, as you might expect, Jason is eager to get out, but can only jump 3 feet high. Not only that, but the walls of the well are covered in slime and so he slips down 2 feet each time he lands.  So, every jump takes Jason 3 ft up but 2 ft back. How many jumps will Jason have to make to get out of the 12ft well?  And before you ask, Jason does not have access to any springs, ladders, or crampons.

Puzzle 6 – Nine dots

Here is the old ‘nine dot’ problem, first popularized around the turn of the last century, and used in lots of creativity training sessions ever since.  Starting from any point and without lifting your pen from the page, can you draw 4 straight lines, such that each of the nine dots has at least one line running through it?

Here is a lesser known variant of the puzzle. Starting from any point and without lifting your pen from the page, can you draw 1 straight line, such that each of the nine dots has the line running through it?

Puzzle 7 – Time for a quickie

Time for a quickie.  What kind of cheese is made backwards?

Puzzle 8 – Sequences

What letter comes next in each of these sequences….

1) W, L, C, N, I, T,_

2) O, T, T, F, F, S,_

3) A, S, D, F, G, H,_

Puzzle 9 – Just between you and me

Can you identify the phrase represented by the following words?

For example…..YOU JUST ME….represents ‘just between you and me’

Try these three:




Puzzle 10 – The Post Office

Imagine waiting in line at the Post Office. There is one person in front of you and another behind. The door suddenly bursts open and in walks a man. He has a bag containing four hats (two white and two black).  The man makes everyone in the line shut their eyes, takes three hats from the bag and placed one on each person’s head. Then he tells you all to look straight ahead and open your eyes, thus ensuring that each of you can only see the colour of any hats directly in front of you.

The man then issues his ultimatum. “First, you are not allowed to say anything to one another. Now, if any of you can correctly state the colour of the hat you are wearing, all three of you will live. However, if you get it wrong then something nasty will happen to all three of you”.

Not surprisingly, you are shocked. After all, you only came in for some stamps and a bar of chocolate. After about a minute of pin-dropping silence you suddenly name the colour of your hat.  There are no mirrors or reflective surfaces in the Post Office, so how did you do it?

Puzzle 11 – Matches and a ball

11 matchsticks and a paper ball are arranged on a table to make the following picture of a dog…

Can you make the dog look in the opposite direction, and still have his tail pointing up, by moving just 2 matchsticks and the paper ball?  Oh, and there are two answers!

Puzzle 12 – More matches

Arrange 9 matchsticks like this….

…now can you move just 3 matchsticks and produce 4 equilateral triangles?  To make things really tricky, no overlapping of the matchsticks is allowed.

Puzzle 13 – Just between you and me again

Can you identify the phrase represented by the following words?

For example…..YOU JUST ME….represents ‘just between you and me’

Try these three:
1) R | E | A | D | I | N | G

Puzzle 14 – He is my son

 A man and his son are involved in a car crash. The father dies on the scene and the son is rushed to hospital. On arrival the surgeon on duty says “I can’t operate on this boy, he is my son!”  How is this possible?

Puzzle 15 – What colour was the bear?

A hunter walks one mile south from his camp. Then he walks one mile west and shoots a bear. Then he walks one mile north, and found himself back at his camp.  What colour was the bear?

I hope that you are enjoying the puzzles.   If you are stumped, or want to check your answers, I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here).

Puzzle 16 – Good morning Erica

 Erica has two children. One of them is a boy.  What is the probability of her other child also being a boy?

Puzzle 17 – Albert’s adventure

My good friend Albert was recently given a job in a clock factory.  On his first day he was asked to construct a clock, and produced the clock shown below. Albert inadvertently created a clock that is different to almost every other clock of this type in the world.  Can you spot why his clock is so unusual?

Puzzle 18 – The further adventures of Albert

Soon after this clock fiasco, Albert was asked to go down to the factory basement and retrieve a rare clock from the company safe.  When he got there he saw the following numbers on the safe door….

77 – 49 – 36 – xx

…the next number in the sequence will open the safe. What number should Albert use to get at the rare clock?

Puzzle 19 – Sta4nce

What phrases are represented here….

1) sta4nce

2) Give Give Give Give Get Get Get Get

3) 1245safety78271

Puzzle 20 – Gone fishing

 Yesterday I went fishing.  I caught a fish that had a length of 30 inches plus half its own length. How long was the fish?

Puzzle 21 – Driving challenge

 As part of a rather odd driving challenge you are required to complete two laps of a racetrack at an overall average speed of 80mph.  At the instant you finish the first lap, you are informed that your average speed over that first lap was only 40mph.  How fast do you need to travel over the second lap to get your overall average speed up to the target value of 80mph?

Puzzle 22 – Out for lunch
Two mothers and two daughters go out for lunch. They order a rectangular pizza and divide it into equal parts with five straight cuts. They then each had an equal share of the pizza.  How is this possible?

Puzzle 23 – Out for more lunch

The following day, 2 mothers and 2 daughters go out for lunch. They order 6 slices of pizza and can share them equally between them.  How is this possible?

Puzzle 24 – Switches and lights

There’s a standard filament-type light bulb in a closed room upstairs. It is controlled by one of three standard on-off switches downstairs. You are downstairs.  How can you discover for certain which switch controls the light by operating one or more switches, and then taking only one trip upstairs into the closed room?

Puzzle 25 – Table tennis

Two boys are playing table tennis.  Their only ball falls off the table and down into a narrow metal pipe in the floor.  The pipe is one foot deep and only just wider than the ball.  Their hands won’t fit into the pipe, and the only tools available are their table tennis paddles and shoelaces.  How can they get the ball out of the pipe?

Puzzle 26 – Storming the castle

A square medieval castle on a square island is under siege. All around the castle there is a square moat 10 meters wide. Unfortunately, a group of raiders have brought footbridges that are only 9.5 meters long.  How can the invaders use their footbridges to invade the castle?

Puzzle 27 – Bacteria

In my laboratory I have a Petri dish that contains a colony of bacteria. Every minute every bacterium divides into two. The colony was started by just one cell at noon. 47 minutes later the Petri dish was half full.  At what time will the dish be full of bacteria?

Puzzle 28 – Splitting the bill

Three men go to a restaurant for dinner and spend £25. Each man gives the waiter £10. The waiter keeps £2 as a tip and gives £1 back to each man.  Thus each man pays £9, and so the group pay £9 x 3 = £27. The waiter keeps £2, making a total of £29.  Where did the missing pound go?

Puzzle 29 – Clocking off

 Can you take the clock face below, and cut it into four pieces such that the numerals on each part add up to the same number?

For example, this solution would not work because the numbers on the four pieces add up to different amounts….

Puzzle 30 – The race

A millionaire tells his two sons to buy two horses and ride to a town 5 miles away. The one whose horse is slower wins and will inherit his fortune. After thinking about the race for days, the brothers ask a wise man for guidance. Upon receiving the advice, they jump on their horses and race to the town as fast as they can.  What did the wise man say to them?

I hope that you are enjoying the puzzles.   If you are stumped, or want to check your answers, I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here).

Puzzle 31 – 10 coins

Arrange 10 coins like this on a table….

Can you move just 2 coins to form 2 lines, each containing 6 coins?

Puzzle 32 – Butts

A man enjoys smoking cigarettes, but doesn’t have enough money to buy them.  However, he realises that if he collects cigarette butts, he can make a cigarette from every 5 butts. So, the man goes around and finds 25 butts.  How many cigarettes can he enjoy as a result?

Puzzle 33 – Secrets and lies

You are in trapped in a room that has two doors.  One is an exit and the other has a hungry lion behind it.  There two people in the room with you. The first is a nice man who always tells the truth and the other is a second hand car salesman who always lies. Both of these people know what is behind each door, but you do not know who is the nice guy and who would sell you a junk car.  You may ask one of the men just one question.  What should you ask in order to escape the room and avoid the hungry lion?

Puzzle 34 – Who is the murderer?

Three men make the following statements regarding a murder that they are suspected of.  Two of the men are lying, and one of them is telling the truth.  Only one of the men committed the crime.

A says: I didn’t do it.
B says: C did it.
C says: A did it.

Which of the three is most likely to be innocent?

Puzzle 35 – Around the earth

Imagine you have a piece of string long enough to stretch around the earth (40,074 km or 4,007,400,000 cm).  Then you take an extra meter of string and add it to the string around the Earth.  Now you spread this extra string around the Earth, supporting it somehow, so that the string forms a circle off the ground.  How high off the ground would the string be?

Puzzle 36 – Triangles

Can you create 8 equilateral triangles with just 6 matches?  You are not allowed to break the matches!

Puzzle 37 – Nostradamus says….

The weird and inaccurate soothsayer Nostradamus once announced…..

“On Wednesday 2nd February 2000, an event will take place for the first time in over 1000 years. In fact, the last time this event happened was 28 August 888″.  For once, he was right. What was the event?

Puzzle 38 – The rope

You have two lengths of rope.  If you set fire to the end of either of them, the rope will burn in exactly one hour. They are not the same length or width as each other.  They also are not of uniform width (they might, for example, be wider in the middle than at the end), thus burning half of the rope is not necessarily going to take 30 minutes.  By burning the ropes, how do you measure exactly 45 minutes worth of time?

Puzzle 39 – More numbers

What number comes next in this series…..


Puzzle 40 – Macy and Preston

Macy and Preston are brother and sister.  They get on well, but have one strange quirk.  They happen to be in the same class at school, and Macy insists on sitting behind Preston, but Preston insists on sitting behind Macy.  How can this seemingly impossible situation be resolved such that both of them are happy?

Puzzle 41 – Symbols

 Can you place a mathematical symbol between 3 and 7 to get a number which is greater than 3 but lesser than 7?

Puzzle 42 – Three triangles

 Three triangles have been made of out three matches apiece…

Can you move just three matches and create exactly five triangles?

Puzzle 43 – The power of love

John and Jane are very much in love, but live a long way apart.  Jane wants to send John a box containing a lock of her hair, but in such a way that no-one can open the box en route.

Both John and Jane each buy a padlock that could secure the box.  However, to avoid discovery, neither John nor Jane can have a key to the padlock that belongs to the other (so Jane cannot have John’s key, and John cannot have Jane’s key).

How can the two lovers create a scheme to ensure that John can open the box when he receives it?

Puzzle 44 – Water and wine

You have two equal sized buckets. One contains water and the other contains the same amount of wine. You transfer a cup of wine to the water bucket and mix it in. Next you transfer a cup of the mixture back to the wine bucket.  Is there more wine in the water, or water in the wine?

Puzzle 45 – My friend, the Devil

Imagine running into the devil.  He leans forward and hands you a cloth bag containing a marble, and explains that the marble inside the bag is either black or white.  He then adds a white marble, shakes the bag, and takes out a marble at random. It’s white.

Then the devil says ‘What are the odds that the remaining marble is white?  Oh, and if you get it wrong, I get your soul’.

What do you say?

Puzzle 46 – The hungry bookworm

A ten-volume set of books are placed upright, in order, on a shelf.  Each book is 4.5 cm thick, and has two covers, each of which are .5 cm thick.  A bookworm starts on page 1 of Volume 1, and munches his way in a straight horizontal line through to the last page of the tenth volume.  What distance does the worm travel?

Puzzle 47 – A riddle

 What can you hold in your right hand, but not in your left?

Puzzle 48 – Balancing equations

Can you make the following equation correct by moving just one matchstick?  There are two answers. Oh, and you are not allowed to use the ‘not equals to’ sign!

Puzzle 49 – More equations

Can you move 1 matchstick and make the equation valid (and you are not allowed to use the ‘not equals to’ sign!).

 I hope that you are enjoying the puzzles.  If you are stumped, or want to check your answers, I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here).

Puzzle 50 – Apples and oranges

You are given three boxes of fruit. One contains just apples, one contains just oranges, and one contains a mixture of apples and oranges.

One box is labelled ‘apples’, one is labelled ‘oranges’, and one is labelled ‘apples and oranges’. None of the boxes is labeled correctly.

Can you label the boxes correctly if you are only allowed to take and look at just one piece of fruit from just one of the boxes?

Puzzle 51 – The race

Two journalists go to an athletics meeting.  There were three contestants in the 100 m race – John, James, and Jack. One journalist reported that John won the race, while James came in second. The other journalist reported that Jack won the race while John came in second.  But you know how unreliable journalists are – in fact, each reporter had given one correct statement and one false statement.

What was the actual placing of the three contestants?

Puzzle 52 – The cannibals

Imagine that you are trekking through a remote jungle and being captured by cannibals. You are brought before the chief and told, “You may now speak your last words. If your statement is true, then we will burn you at the stake. If your statement is false, we will boil you in oil.”  Logically, what statement can you make to ensure that the cannibals have to let you go?

Puzzle 53 – Stop the crying babies

 Imagine that there are nine babies on a hospital ward.

Unfortunately, they are all crying their heads off because they are suffering from colic.  You are given permission to order two sound proofed screens, each of which is in the shape of a square, and asked to arrange the screens in such a way as to ensure that each baby is isolated from all of the others.  The square screens can be any size you like.  Can you solve the problem?

Puzzle 54 – Feathers

 You are drugged and wake-up in a locked room with a man. There is a table in the room and there are 11 feathers on the table. A voice booms over a loudspeaker explaining that the two of you are going to take turns removing feathers from the table. Each time you and the other chap can choose to take either one, two or three feathers. Whoever ends up taking the final feather from the table will be shot.  You get to go first – how many feathers should you take from the table?

Puzzle 55 – 12 matchsticks

 Take 12 matches and use 8 of them to create a square like this…..

Can you use the 4 extra matches to divide the square into 2 parts, where each part has the same shape and area? And no stacking up of the matchsticks!

Puzzle 56 – The combination

Imagine that you are trapped in a prison cell.  The only way out is through the door, but the door is locked.  There is a combination lock on the door, and the following sequence of numbers appears above the lock:


…to open the door you have to enter the next number in the sequence into the combination lock.  What number should you enter?

Puzzle 57 – Time for pasta

 I have to make dinner and have to boil some pasta for exactly 9 minutes.  However, I only have two hourglasses.  One of them measures 7 minutes and the other measures 4 minutes.  Can I use the hourglasses to time exactly 9 minutes?

Puzzle 58 – Yes, no, don’t know

Once again, you are trapped in a prison and the guard decides to play a game.  If you win, you will be allowed to leave.  But if you lose, you die.   The guard says that he is thinking of Number 1, Number 2, or Number 3.  You are allowed to ask one question to find out which of these three numbers the guard has in mind. However, the guard will only answer with a “yes”, “no”, or “I don’t know”.  What should you say to the guard?

Puzzle 59 – The bike ride

The other day I went for a bike ride.  My favourite route has signs every meter saying how far you have travelled.  I came across the sign saying ’15951 meters’ and thought ‘Oh, that’s interesting, it is a number palindrome because it reads the same from left to right as right to left’.  Then I rode on.  Two hours later I came across the next palindromic number sign.  How fast was I going?

Puzzle 60 – The lance

A knight arrives at a castle carrying a lance that is five feet long.  The guard tells him that no-one is allowed in the castle with an object that is over four feet long.  The knight is a tad upset, but then has an idea.  He goes into town, finds the local carpenter and asks him to make something.  The knight then returns to the castle and the guard lets him in.

Due to his clever thinking, the knight finds himself inside the castle with his lance.  The lance is fully functioning, and has not been cut in any way.

How is this possible?

I hope that you are enjoying the puzzles.   If you are stumped, or want to check your answers, I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here).

Puzzle 61 – My pet monkey

I want to give my pet monkey a cup of banana juice.  I have a big vat of the stuff (don’t ask), but can only give him exactly 4 fluid ounces (any less and he gets angry, any more and he dies).  However, the really bad news is that I have a cup that will contain 5 fluid ounces when full and another one that contains 3 fluid ounces when full.

How can I use the two cups to measure exactly 4 fluid ounces and so keep the monkey happy?

Puzzle 62 – A or B

Here are three answers:
A) Answer A
B) Answer A or B
C) Answer B or C

There is only one correct answer to this question. Which answer is this?

Puzzle 63 – 10 matchsticks

Here are ten matchsticks making up an equation based on Roman numerals….

Can you move 1 matchstick and make the equation correct?  You are not allowed to remove the matchstick completely and can’t leave any blanks (e.g., XI +   = XI isn’t allowed).   One solution is very simple and another is very sneaky.


Puzzle 64 – Even more matchsticks

Can you rearrange 6 matchsticks to leave nothing?

Puzzle 65 – Can you make 100?

How can you place the arithmetical signs ‘+’ and ‘-’ between the consecutive numbers 123456789 so that the end result is 100?

So, for example, you could go…..

12+34+56-7-89 , but that would make 6, so that doesn’t work.

Puzzle 66 – Cat

Which side of a cat contains the most hair?

Puzzle 67 – Time for tea

Yesterday I saw a drinks machine that had three selections – Tea, Coffee or Random (Tea or Coffee).  However, the machine was wired up wrongly so that each button does not give what it claims.

If each drink costs 50p, what is the minimum that you have to put into the machine to work out which button gives which selection?

Puzzle 68 – The land

How can you divide this piece of land into four equally shaped pieces?

Puzzle 69 – Is it it is

Can you punctuate the words in the sentence below so that they make sense?  Most of the words are not shown capitalized so as not to give any hints as to the beginning or ending of the sentences.

That that is is that that is not is not is it it is

Puzzle 70 – The 10 sheep

A friend of mine has 10 sheep, and they insist on standing in a circular pen like this…..

However, it turns out that all of the sheep don’t like one another, and so have also insisted that they are protected from each other by a wall.  The problem is that sheep pen walls are circular, and my friend can only afford three of them.  How can you draw three circles on the illustration to ensure that each of the sheep has its own space, protected from the others?

Puzzle 71 – Two trains

I have some train tracks very close to my house.  Everyday I go down to the tracks and wait for a train to pass.  There are two types of train – passenger trains and freight trains.  I have been going down to see the trains at random times for a few months now and 90% of the time I see a passenger train.  So far, so what?

Well, the other day I met the man in charge of the line, and he told me that 50% of the trains on the line are passenger trains and the other 50% are freight trains.  How can this be the case?

Puzzle 72 – Strange rules

According to my strange rule, 4 is half of 9, 6 is half of 11, and 7 is half of 12.

Can you work out the rule, and so say what half of 13 is?

Puzzle 73 – 2 squares, 4 triangles

Can you make 2 squares and 4 triangles from just 8 matches?  You are not allowed to bend or break any of the matches!

Puzzle 74 – Had had had

Can you punctuate the words in the sentence below so that they make sense?  Most of the words are not shown capitalized so as not to give any hints as to the beginning or ending of the sentences.

James while John had had had had had had had had had had had a better effect on the teacher

Puzzle 75 – Pebbles

John has a problem.  He has been handed 7 pebbles by a friend and told that he has to arrange them so that there are 6 straight lines of pebbles, with each line containing 3 pebbles.  If John cannot solve the puzzle then his friend will murder him.  Can you help prevent John being murdered?

Puzzle 76 – Boxes

You have a large box, a small box, and three stones…..

How can you put the stones in the boxes to ensure that each box contains an odd number of stones?  There are at least two solutions – can you find both of them?

Puzzle 77 – Mr Pythagoras

This nice puzzle was submitted by my good friend Mr Pythagoras.  Take a look at the diagram below….

Can you figure out the radius of the circle?

Puzzle 78 – More rules

What rule has been used to create the following number sequence:

8 5 4 9 1 7 6 3 2 0

Puzzle 79 – Cat

Can you change 100 into CAT by moving just two of these matchsticks?

Puzzle 80 – The children

Let’s suppose that a couple have four children.  All four of the children could be the same sex, there could be three of one sex and one of another, or the sexes could be balanced two and two.  Which possibility is most likely?

Puzzle 81 – The prison cell

Imagine being locked in a dark dank cell.  There is a computer screen and a keyboard in the cell with you, and that allows you to type and submit any word you like.  The computer is linked to the door of the cell, and certain words will open the door.

On the wall a helpful prisoner has left the following 3 clues:

What word would you type into the computer?  There are quite a few possible answers!

Puzzle 82 – Move one number

Can you make the following equation correct by moving just one number…..

62 – 63 = 1

Puzzle 83 – The chemicals

What chemical compound is represented by the following…


Puzzle 84 – Large and small

What is the largest number you can get using only 2 digits?

Puzzle 85 – Cars and the fly

Two cars are approaching each other at a constant velocity of 60mph.  When the cars are two miles apart, a very fast fly leaves the front bumper of one of the cars and travels towards the other at the speed of 120mph. Upon reaching that car, the fly immediately reverses direction. This continues until the cars collide.

How far did the fly travel?

Puzzle 86 – At the zoo

Yesterday I met a zookeeper.  I asked him how many birds and beasts he had in his zoo.  He told me that there were 30 heads and 100 feet in his zoo.  How many birds and beasts does he have, assuming that all birds have two feet and all beasts have 4 feet?

Puzzle 87 – Socks

I have 45 socks in my drawer.  There are 14 identical blue, 24 identical red and 7 identical black.  Yesterday all of the lights went in my house, so now I live in complete darkness.  How many socks do I need to take out of the drawer to ensure that I have a pair of each colour?

Puzzle 88 – Reindeer race

One day Santa was bored and so decided to entertain himself by racing some of his reindeer.  The first 100 meter race was between Dasher and Dancer, and Dasher won by 10m.  The next 100 meter race was between Dancer and Prancer, and Dancer won by 10m.  Finally, Dasher ran against Prancer in another 100m race.  By how many meters did Dasher win?

Puzzle 89 – Children and numbers

Last night I went to a party.  There were 8 children there and they all happened to be wearing black sweaters.  My uncle gathered them together, found some chalk, and wrote one number on the back of each child.

The numbers were: 1, 2, 3, 4, 5, 7, 8, 9.  My uncle then asked whether it was possible to arrange the children into two groups of four, such that the numbers on the backs of the children in each group came to the same total.  After much messing around, we managed it.  Can you?

Puzzle 90 – Sticks and stones

I have a few thousand sticks.  Each of them is 1 metre long.  The other day I decided to break each of the sticks in two, with each of breaks happening at a random position along each stick.

What is the average length of the shorter pieces?

Puzzle 91 – Missing number

What’s the missing number….

Puzzle 92 – The Bible

According to the Bible, who killed 25% of the world’s population?

Puzzle 93 – Palindromes

In what sense is this order of the numbers from 1 to 10 palindromic, (that is, reading the same from left to right as right to left)?

1   4   3   5   10   2   6   9   8   7

Puzzle 94 – In the library

In one of the books I own the end is in the first half, and the prefix in the second half.  The foreword comes after the epilogue, but the index comes before the introduction.  What is the book?

Puzzle 95 – The cute puppy

You have been captured by a small cute puppy.   He has two identical opaque vases, and 100 white beads and 100 black beads.  The puppy will allow you to arrange all of the beads in whatever way you like between the two vases, but neither of the vases can be empty.  The puppy will then close his eyes, put his little paw into one of the vases, rummage around, and remove just one bead.  You have no idea which vase he will choose.  If the puppy chooses a black bead, you will be allowed to stroke his head.  But if he chooses a white bead he will bite you.  How do you arrange the beads to give yourself the best chance of getting a stroke?

Puzzle 96 – Erica and John

Erica and John are standing in the same cattle field at the same time. Erica can see the same number of bulls and cows in the field. However, John can see twice as many cows as bulls.

How can this be and how many cows and bulls are there in the field?

Puzzle 97 – More chemicals

What five letter chemical element is represented by this list…


Puzzle 98 – Largest numbers

If you rotate the number 6 by 180 degrees you get the number 9.  What is the largest increase possible by rotating a number by 90 degrees?

Puzzle 99 – Monday, Tuesday

Jimmy’s mother had 4 children. She named the first Monday, the second Tuesday and the third Wednesday.

What is the name of the fourth child?

Puzzle 100 – How much?

I went into a shop and this is how the conversation went:
Me: “How much does it cost for one?”
Assistant: “£2″
Me: “And how much for 10?”
Assistant: “£4″
Me: “How much for 100?”

What was I buying?

Puzzle 101 – Letters and letters

The letters of the alphabet can be grouped into 4 distinct categories.  According to these categories, the first 13 letters of the alphabet would be classified as follows:

Category 1: AM

Category 2: BCDEK

Category 3: FGJL

Category 4: HI

I hope that you have enjoyed the puzzles.   If you are stumped, or want to check your answers, I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here).


  1. Your answer to puzzle 16 is incorrect. You say that the answer is 1 in 3 but you are not counting the boy boy scenario twice as you should because it is not specified that the know boy was born first or second, there for there is a boyA and boyB scenario or a boyB boyA scenario. If you count boy girl and girl boy as two seperate scenarios you have to count the boy boy scenario twice. Therefore the answer is 2 out of 4 or 1/2 just as statistics reasoning would state. The second child being a boy has a 50/50 coin flip of being a boy. Knowing one childs sex does not change that.

  2. It’s disappointing to find that many of the clarifications made on this blog to the above puzzles did not find their way into the book.

    For example, to solve puzzle 45 we need to know the probability that the initial marble in the cloth bag is white. Prof. Wiseman admitted as much in the answer posted on this blog (since deleted), yet this point is not mentioned above or in the book.

    Similarly, the answers in the book do not touch on any of the ambiguities and subtleties discussed in the answers (now deleted) on this blog. A missed opportunity.

  3. I have been looking for a solution to a shape puzzle for 30 years!!!
    Do you perhaps know?

    A rectangle with one horizontal line through the middle – two vertical lines seperating the top section into 3 even space and 0ne line separating the bottom section into 2 even spaces.

    Draw a single line which crosses each line once and only once!!

    1. The line can’t be straight. you can draw a line through the top two lines, cross the horizontal line and then through the bottom line.

  4. Hi Richard,
    Enjoyed your talk at EMC.

    I’d love to hear your thoughts on the psychotherapeutic benefits of magic. I’m currently putting togehter a continuing ed course for psychologists on this topic. It’s fascinating what has been done with various “magic therapy” programs around the world.

    Ron Porter, Ph.D.

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