MathsJam, 17 November 2015

A few links from last night’s meeting:

Chalkdust magazine. Includes their excellent crossnumber.

Geometry puzzle. Via Alison Kiddle.

Five 3-4-5 triangles. I think the challenge is to arrange the five equal-sized triangles into a symmetrical shape: reference.


Next meeting: Tuesday 15 December


MathsJam meeting 24 March 2015

A quiet meeting this time.

One regular MathsJammer popped in briefly before heading off to Portsmouth Cafe Scientifique. (I do recommend CafeSci, at least when it doesn’t clash with MathsJam. You can follow them on twitter @portscafesci.)

Jack1 arrived with an interesting pdf on recreational mathematics. We noted particularly that Southsea promenade matches one of the symmetry classes from the last article therein.

Andy arrived later and we all tried this geometry puzzle, which involves a circle and a square, but turns out to also involve a hidden triangle.

Andy had brought along Perudo, so we settled into a couple of three-handed games to complete the evening.

Interesting tweets:

5 points in a rectangular grid:

Conway’s Game of Life meets Blokus:

MathsJam meeting 17 February 2015

The latest Portsmouth MathsJam meeting was attended by 11 people, which we think is a record number, and included two new and very welcome attendees, Ruth and James.

Jack1 (there were two Jacks attending) had brought along some coin sliding puzzles which were designed by Bob Hearn and originally appeared on the website way back in December 2005. They can be found on this page (scroll down to the entries for 04 December). We decided these were much trickier than they looked, but Ruth persevered and found a perfect solution for the 66 move puzzle.

Meanwhile, several MathsJammers were attempting some other physical puzzles including the Bedlam Cube, which James managed to solve, and Rubik’s 360 which, sadly, was beyond anyone that attempted it. (The Bedlam Cube is quite a well known puzzle and once appeared on Dragons’ Den: YouTube link.)

As usual, the MathsJam Twitter feed had some interesting puzzles including a point in a square problem from Alison Kiddle, and a cow tethered in a circular field problem. I subsequently found this latter question, with solution, on math.stackexchange.

Finally, we settled down to an old favourite: Perudo. We played mostly in pairs and after a close contest Judy/Gabor edged out Jack1/Nick (a.k.a. PerudoJedi), with Andy a close third.

Overall, this was definitely one of our busiest and most enjoyable MathsJam meetings.

MathsJam meeting 18 November 2014

One of the great things about MathsJam is that you can bring along anything even remotely maths connected for people to try. Games, puzzles, quizzes and general maths problems are all regularly brought along. Here are some of the things I tried at the latest meeting.

Jack produced another Only Connect-style maths quiz and much time was spent pondering the answers to the clues.

Jack also had some algebra questions. Lots of algebra questions! I particularly liked this one:


Show that the coefficient of the x^{-12} term of the above expression is -15.

The MathsJam Twitter feed contained several interesting questions:

  • What is the sum of the digits of the sum of the digits of the sum of the digits of 2014^{2014}? It was claimed that this could be solved with “only primary-school maths facts”, although we couldn’t find an easy solution ourselves.
  • Show that 1 and 9 are the only square numbers composed entirely of odd digits. We did manage an acceptable proof of this.
  • What is the shortest line that bisects an equilateral triangle? The line need not be straight.


MathsJam meeting 21 October 2014

The regular monthly meeting of Portsmouth MathsJam was held, as usual, at the King Street Tavern in Southsea. There was a welcome return for Andy, who has recently moved back to the region, and there were eight MathsJammers in total.

Most of the evening was spent trying various puzzles from a collection called Brain Busters that Jack had brought along. The puzzles were created by Ed Pegg Jr and you can find a pdf of them all at

(We very much recommend Ed Pegg Jr’s site It has a huge collection of maths-related puzzles and links.)

Our own Edd posed this puzzle: consider two triangles with side lengths 5, 5, 6 and 5, 5, 8 respectively. What is the ratio of their areas? Before you go digging up your old book of trigonometric formulas, there is a simple way to find the solution.

Finally, we also enjoyed seeing the photos of other MathsJammers constructing cubes for the MegaMenger project. See for more information, or search @megamenger or #megamenger on Twitter for many pictures.

MathsJam meeting 23 September 2014

Portsmouth MathsJam continues to be held on the second-to-last Tuesday of each month at the King Street Tavern, with the most recent meeting held on 23 September.

It was a fairly quiet meeting with just four of us for most of the evening, though some late arrivals boosted the number to seven. Jack brought along an Only Connect-style maths quiz and we tried several puzzles from the MathsJam twitter feed and elsewhere.

Here are tweets of some of the maths puzzles we enjoyed this month:

20th November means MathsJam Novemtory…

We had a great time completing our Novemtory form, Brian paced the Pub to enable a reasonable estimate of the number of ping pong balls to fill the room.  Although none seemed particularly serious when it came to ages and demographic split…

We also had important business to deal with during this MathsJam session:  finalising our choices for the Portsmouth MathsJam Christmas meal which is being held on 12.12.12.  We have moved the date a bit – but it is not the first time that Portsmouth MathsJam is out of sync with the others.  The King Street Tavern has a delicious Christmas  menu which we are looking forward to sampling.

Nick produced an excellent puzzle, which kept us happy for quite a while but unfortunately mine got wet (beer!) and so I no longer have an official record  of it.  Suffice it to say it was a series of 4 numbers and using the usual operators (only) we had to decide which number(s) 1-20 it would not be possible to make.

In view of Matt’s plans for Rubik’s cube the following day we had a bit of a go with a Rubik’s cube, Hungarian Ring and Bedlam Cube.  The Bedlam Cube remains unsolved and will be back…

There was also a MathsJam outing this week:  24th November Robin Ince appeared at The Spring in Havant.  Five MathsJammers went along and had an excellent night.

If anybody would still like to come to the Christmas meal just pop into the King St Tavern and have a chat with Sam to choose what you would like to eat and pay a small deposit.

The menu may be viewed through the link to King St Tavern.