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Prime Permutations

Friday 1st February 2019

Think of all the ways of arranging the digits one to nine to make nine-digit numbers. How many of these nine-digit numbers are prime? It is not half as difficult as you may think!

That’s your puzzle of the month for February and the answer is at the end of this newsletter. While you are thinking about it I will run through the most notable new additions to the Transum website last month.

Pick the Primes

Pick The Primes is an addictive challenge to distinguish between prime and composite numbers as quickly as possible. The activity encourages you to improve on your personal best time for each of the levels containing increasingly large numbers. A great, fun idea for the last ten minutes of your Maths lesson.

Linear Programming is now ready online for pupils to use to practise forming inequalities from real-life situations. It makes use of the Desmos graph plotter to produce the colourful shaded regions. There are five levels plus a link to exam-style questions.

Factor Tree Puzzles have been added to the very popular Factor Trees interactive exercise. I suppose it is the way the trees grow according to the factors entered that makes this exercise so much better than the equivalent exercise from a textbook.

Snappy Sorting will give pupils some idea of how the algorithms used by modern technology work. They could use a bubble sort to order the numbers but is this the fastest method? Over two thirds of the people to visit this activity then go on to claim a trophy for completing it. The activity has become quite popular already.

Missing Lengths is not new but it has been expanded and the questions have now been arranged into more levels in a more logical order. There are four levels plus a link to exam-style questions.

Algebraic Perimeters is brand new and provides lots of practice answering the type of question that I notice more frequently appearing on GCSE exam papers.

Estimating Correlation is not for everyone. It was written specifically as a reminder for some of my older pupils who are learning about scatter graphs and appreciated a variety of different learning opportunities.

Surface Area has just been expanded. It is more of a traditional, four-level exercise beginning with a face counting level leading on to some tricky puzzles in level 4.

Valentine’s Day falls in February and if you want to prove that you are a real trendy teacher you could surprise your pupils with one of two Valentine-themed Starters on the 14th: Valentine’s Puzzle and Love Maths.

I have included two audio clips in the podcast version of this newsletter that I have found in other podcasts I listen to. The first is from Freakanomics episode 247 in which Tom Whipple who has consulted an army of preposterously overqualified experts to find the secret to winning any game. I was particularly interested to hear him talk about games similar to two activities on the Transum website: Shark’s Dinner and Code Cracker.

The games involve guessing letters in hidden words as in the classic hangman game. I have always started with the letters e, t and a as these are the most common letters in English. I learned from the podcast though that three letter words do not have the same expected letter probabilities as four letter words. Have a listen to the podcast then try one of the Transum activities with this new information to help you.

The other audio clip I have included in the podcast is that of one of my favourite comedians, Frank Skinner, talking about the Royal Game of UR. The Transum Remainder Race is based on this ancient board game so my ears pricked up when I heard him joking about it.

For future reference there are two ‘mirror’ sites that contain all the Transum Starters and activities. They are at and The only difference is that they don’t contain the details of your Transum subscription account so you won’t be able to log in there. If it looks like will be offline for a long time then I will transfer the database containing your details to so you will eventually be able to log in there too.

Thanks so much for you feedback, comments and suggestions. If it wasn’t for the messages I get from people using the Transum website I might start to feel quite lonely. It’s great to hear how you have used the puzzles with your pupils and it’s also nice (but quite rare) to hear from someone who has spotted a mistake or a typo on one of the web pages. Keep the feedback coming! I really appreciate it.

The solution to this month’s puzzle is none! None of the nine-digit numbers are prime because all of them will be divisible by three. This is a good time to look at the divisibility tests to remind yourself that if the sum of the digits in a number is divisible by three, then the number itself is divisible by three. Adding gives a digit sum of 45 which is of course fifteen times three.

That's all from me.


PS. What do you call a number that can’t keep still?

Answer: A roamin’ numeral.

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