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map projections error bars london underground manchester science festival the aperiodical ternary martin gardner dates php game show probability logic raspberry pi machine learning binary graph theory matt parker coins folding tube maps programming weather station football rugby mathslogicbot puzzles craft interpolation data royal baby noughts and crosses stickers geometry javascript triangles books sound curvature christmas card approximation flexagons chebyshev countdown dragon curves chess world cup nine men's morris frobel mathsteroids sorting sport light video games misleading statistics games reddit braiding draughts menace oeis palindromes game of life speed plastic ratio electromagnetic field final fantasy hexapawn python arithmetic golden spiral pythagoras fractals christmas pizza cutting harriss spiral chalkdust magazine bubble bobble wool bodmas realhats reuleaux polygons accuracy latex a gamut of games rhombicuboctahedron tennis news estimation polynomials gerry anderson cross stitch folding paper twitter captain scarlet national lottery trigonometry london go people maths platonic solids propositional calculus dataset european cup asteroids golden ratio manchester statistics radio 4 probability hats inline code pac-man aperiodical big internet math-off**2018-07-07**

## World Cup stickers 2018, pt. 3

So you've calculated how much you should expect the World Cup sticker book to cost
and recorded how much it actually cost. You might be wondering what else you can do with your sticker book.
If so, look no further: this post contains 5 mathematical things involvolving your sticker book and stickers.

### Test the birthday paradox

In a group of 23 people, there is a more than 50% chance that two of them will share a birthday. This is often called the birthday paradox, as the number 23 is surprisingly small.

Back in 2014 when Alex Bellos suggested testing the birthday paradox on World Cup squads, as there are 23 players in a World Cup squad. I recently discovered that even further back in 2012, James Grime made a video about the birthday paradox in football games, using the players on both teams plus the referee to make 23 people.

In this year's sticker book, each player's date of birth is given above their name, so you can use your sticker book to test it out yourself.

### Kaliningrad

One of the cities in which games are taking place in this World Cup is Kaliningrad. Before 1945, Kaliningrad was called Königsberg. In Königsburg, there were seven bridges connecting four islands. The arrangement of these bridges is shown below.

The people of Königsburg would try to walk around the city in a route that crossed each bridge exactly one. If you've not tried this puzzle before, try to find such a route now before reading on...

In 1736, mathematician Leonhard Euler proved that it is in fact impossible to find such a route. He realised that for such a route to exist, you need to be able to pair up the bridges on each island so that you can enter the island on one of each pair and leave on the other. The islands in Königsburg all have an odd number of bridges, so there cannot be a route crossing each bridge only once.

In Kaliningrad, however, there are eight bridges: two of the original bridges were destroyed during World War II, and three more have been built. Because of this, it's now possible to walk around the city crossing each bridge exactly once.

I wrote more about this puzzle, and using similar ideas to find the shortest possible route to complete a level of Pac-Man, in this blog post.

### Sorting algorithms

If you didn't convince many of your friends to join you in collecting stickers, you'll have lots of swaps. You can use these to practice performing your favourite sorting algorithms.

#### Bubble sort

In the bubble sort, you work from left to right comparing pairs of stickers. If the stickers are in the wrong order, you swap them. After a few passes along the line of stickers, they will be in order.

In the insertion sort, you take the next sticker in the line and insert it into its correct position in the list.

In the quick sort, you pick the middle sticker of the group and put the other stickers on the correct side of it. You then repeat the process with the smaller groups of stickers you have just formed.

### The football

Sticker 007 shows the official tournament ball. If you look closely (click to enlarge), you can see that the ball is made of a mixture of pentagons and hexagons. The ball is not made of only hexagons, as road signs in the UK show.

Stand up mathematician Matt Parker started a petition to get the symbol on the signs changed, but the idea was rejected.

If you have a swap of sticker 007, why not stick it to a letter to your MP about the incorrect signs as an example of what an actual football looks like.

### Psychic pets

Speaking of Matt Parker, during this World Cup, he's looking for psychic pets that are able to predict World Cup results. Why not use your swaps to label two pieces of food that your pet can choose between to predict the results of the remaining matches?

### Similar posts

World Cup stickers 2018, pt. 2 | World Cup stickers 2018 | World Cup stickers | Euro 2016 stickers |

### Comments

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**2017-11-14**

## MENACE at Manchester Science Festival

A few weeks ago, I took the copy of MENACE that I built to Manchester Science Festival, where it played around 300 games against the public while learning to play Noughts and Crosses. The group of us operating MENACE for the weekend included Matt Parker, who made two videos about it. Special thanks go to Matt, plus
Katie Steckles,
Alison Clarke,
Andrew Taylor,
Ashley Frankland,
David Williams,
Paul Taylor,
Sam Headleand,
Trent Burton, and
Zoe Griffiths for helping to operate MENACE for the weekend.

As my original post about MENACE explains in more detail, MENACE is a machine built from 304 matchboxes that learns to play Noughts and Crosses. Each box displays a possible position that the machine can face and contains coloured beads that correspond to the moves it could make. At the end of each game, beads are added or removed depending on the outcome to teach MENACE to play better.

### Saturday

On Saturday, MENACE was set up with 8 beads of each colour in the first move box; 3 of each colour in the second move boxes; 2 of each colour in third move boxes; and 1 of each colour in the fourth move boxes. I had only included one copy of moves that are the same due to symmetry.

The plot below shows the number of beads in MENACE's first box as the day progressed.

Originally, we were planning to let MENACE learn over the course of both days, but it learned more quickly than we had expected on Saturday, so we reset is on Sunday, but set it up slightly differently. On Sunday, MENACE was set up with 4 beads of each colour in the first move box; 3 of each colour in the second move boxes; 2 of each colour in third move boxes; and 1 of each colour in the fourth move boxes. This time, we left all the beads in the boxes and didn't remove any due to symmetry.

The plot below shows the number of beads in MENACE's first box as the day progressed.

You can download the full set of data that we collected over the weekend here. This includes the first two moves and outcomes of all the games over the two days, plus the number of beads in each box at the end of each day. If you do something interesting (or non-interesting) with the data, let me know!

### Similar posts

MENACE | Building MENACEs for other games | MENACE in fiction | The Mathematical Games of Martin Gardner |

### Comments

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**2017-11-22**

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**2015-03-24**

## Tube map stellated rhombicuboctahedron

A while ago, I made this (a stellated rhombicuboctahedron):

Here are some hastily typed instructions for
Matt Parker, who is making one
at this month's Maths Jam. Other people are
welcome to follow these instructions too.

### You will need

- 48 tube maps
- glue

### Making a module

First, take a tube map and fold the cover over. This will ensure that your
shape will have tube (map and not index) on the outside and you will have
pages to tuck your tabs between later.

Now fold one corner diagonally across to another corner. It does not matter
which diagonal you chose for the first piece but after this all following pieces
must be the same as the first.

Now fold the overlapping bit back over the top.

Turn it over and fold this overlap over too.

You have made one module.

You will need 48 of these and some glue.

### Putting it together

By slotting three or four of these modules together, you can make a
pyramid with a triangle or square as its base.

A stellated rhombicuboctahedron is a rhombicuboctahedron with a pyramid, or
stellation on each face. In other words, you now need to build a
rhombicuboctahedron with the bases of pyramids like these. A rhombicuboctahedron
looks like this:

en.wiki User Cyp, CC BY-SA 3.0

More usefully, its net looks like this:

To build a stellated rhombicuboctahedron, make this net, but with each shape
as the base of a pyramid. This is what it will look like 6/48 tube maps in:

If you make on of these, please tweet me a photo so I can see it!

### Similar posts

Tube map Platonic solids, pt. 2 | Tube map kaleidocycles | Tube map Platonic solids, pt. 3 | Electromagnetic Field talk |

### Comments

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2019-03-08Matthew