Transum Software

Trafalgar Square

Solve the number puzzles drawn on the pavement of Trafalgar Square in London.

In London's Trafalgar Square a young man from Slovakia captures the interest of passers-by with puzzles he's drawn with chalk on the pavement.

Chalk drawn puzzles

Above the puzzles were the only instructions:

Trafalgar Square Instructions

When I returned the following week all nine levels were ready for the keen puzzle solvers.

Trafalgar Square Puzzles

Can you explain how to find the missing number in each of the grids in the photograph above? The first few levels are quite easy but then it gets difficult. The answers are available lower down this page for subscribers (except the answer to level 8 which I'm still trying to figure out).

There are some easier 'Trafalgar Square' grids below for you to complete. They contain fixed rules but randomly-generated numbers. You can see how well you are doing by clicking the check button as often as you like as you work through the levels. If you get a level wrong try again:

Level 1


Correct Wrong

Level 2


Correct Wrong

Level 3


Correct Wrong

Level 4


Correct Wrong

Level 5


Correct Wrong

Level 6


Correct Wrong

Level 7


Correct Wrong

Level 8


Correct Wrong

Level 9


Correct Wrong


Do you have any comments about this exercise? Can you do level 8 in the third photograph on this page? Do you enjoy working on the puzzles on the Transum website? Please let me know by entering a comment here.


Lemon Law

Lemon Law

Change the numbers on the apples so that the number on the lemon is the given total.

The short web address is:


Nine Digits

Nine Digits

Arrange the given digits to make three numbers such that two of them add up to the third.

The short web address is:




Place the numbers one to nine in the table so they obey the row and column headings.

The short web address is:


The creators of the Trafalgar Square puzzles have made contact and kindly provided the photographs below:

Kardos photograph 1

Peter Kardos and Daniel Kardos, creators of the Trafalgar Square puzzles

Kardos photograph 2 Kardos photograph 3 Kardos photograph 4

This web site contains over a thousand free mathematical activities for teachers and pupils. Click here to go to the main page which links to all of the resources available.

Please contact me if you have any suggestions or questions.

Email address

Mathematicians are not the people who find Maths easy; they are the people who enjoy how mystifying, puzzling and hard it is. Are you a mathematician?

Comment recorded on the 16 March 'Starter of the Day' page by Mrs A Milton, Ysgol Ardudwy:

"I have used your starters for 3 years now and would not have a lesson without one! Fantastic way to engage the pupils at the start of a lesson."

Comment recorded on the 1 May 'Starter of the Day' page by Phil Anthony, Head of Maths, Stourport High School:

"What a brilliant website. We have just started to use the 'starter-of-the-day' in our yr9 lessons to try them out before we change from a high school to a secondary school in September 2007. This is one of the best resources on-line we have found. The kids and staff love it. Well done an thank you very much for making my maths lessons more interesting and fun."

Featured Activity

Where's Wallaby?

Where's Wallaby?

Find the hidden wallaby using the clues revealed at the chosen coordinates. Not only is this a fun way to practise using coordinates it is also a great introduction to Pythagoras' theorem and loci.


There are answers to this exercise but they are available in this space to teachers, tutors and parents who have logged in to their Transum subscription on this computer.

A Transum subscription unlocks the answers to the online exercises, quizzes and puzzles. It also provides the teacher with access to quality external links on each of the Transum Topic pages and the facility to add to the collection themselves.

Subscribers can manage class lists, lesson plans and assessment data in the Class Admin application and have access to reports of the Transum Trophies earned by class members.

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Go Maths

Learning and understanding Mathematics, at every level, requires learner engagement. Mathematics is not a spectator sport. Sometimes traditional teaching fails to actively involve students. One way to address the problem is through the use of interactive activities and this web site provides many of those. The Go Maths main page links to more activities designed for students in upper Secondary/High school.


If you found this activity useful don't forget to record it in your scheme of work or learning management system. The short URL, ready to be copied and pasted, is as follows:

Do you have any comments? It is always useful to receive feedback and helps make this free resource even more useful for those learning Mathematics anywhere in the world. Click here to enter your comments.


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Description of Levels



Exam Style questions are in the style of GCSE or IB/A-level exam paper questions (worked solutions are available for Transum subscribers).

More on this topic including lesson Starters, visual aids, investigations and self-marking exercises.

Answers to this exercise are available lower down this page when you are logged in to your Transum account. If you don’t yet have a Transum subscription one can be very quickly set up if you are a teacher, tutor or parent.

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You may also want to use a calculator to check your working. See Calculator Workout skill ##.

Don't wait until you have finished the exercise before you click on the 'Check' button. Click it often as you work through the questions to see if you are answering them correctly. You can double-click the 'Check' button to make it float at the bottom of your screen.

Answers to this exercise are available lower down this page when you are logged in to your Transum account. If you don’t yet have a Transum subscription one can be very quickly set up if you are a teacher, tutor or parent.

Log in Sign up