** MATHEMATICS IS COLORFUL**

- Visual Mathematical Dictionary a collaborative project to break down language barriers
- PROPORTIONATE a user-friendly proportion calculator (partners wanted)

There are no repetitions (you do not need 7x6 if you know 6x7) and there is no multiplication by 1. The dedicated webpage contains colorful images for posters and mugs (and also a Factorization Poster).

A clock to learn the Chinese Remainder Theorem. The dedicated webpage with articles and animations.

- PLIMPTON 322: with Deborah Stranen, the article
*Converting the Old Babylonian Tablet ‘Plimpton 322’ into the Decimal System as a Classroom Exercise*in Convergence and related slides.

A geometric construction for the gcd and the lcm.

- The article in Plus Magazine and some slides.
- The article in Recreational Mathematics Magazine, with Joe Reguengo da Sousa and Sebastiano Tronto.
- One result with Bruno Carvalho da Veiga pdf.

Understanding Knuth's algorithm for winning Mastermind.

- The article in The College Mathematics Journal, with Thomas M. Fiore and Alexander Lang
- The Master Mind wheel and some slides.

- The article The hardest logic puzzle ever in Plus Magazine.
- With Jerry Hilgert,
*Riddelicious*, mathematical riddles set in the Luxembourgish context, in English, German, French. - With Lisa Vagnozzi,
*Dodici Storie Fantastiche*, 12 short stories based on mathematical riddles.

- Mathematical exploration of the Vichten Roman mosaic.
- Junior BINGO, with cards for the MINI-BINGO.
- Rubik's Cube, when your student becomes World Record Holder.
- with Pit Ronk, Beware proportions, collecting some reflections about proportions.
- Multiplication Table Puzzle, an activity for the elementary school.
- Sim!Cong!, a didactical card game for learning the Congruence and Similarity Theorems for triangles.
- with Edith Wittman, Drehoskop, a tool to detect rotational symmetries for polyhedra.
- PytEuk, an puzzle for Pythagoras' Theorem.
- 135, a puzzle with two formulas related to the number 135, .
- with Pietro Sgobba and Sebastiano Tronto, Proof without words images.
- Beat the Prof: Ebene Geometrie, Quiz for Zeit Online.
- Mockingjay Mathematics exercise sheet.
- with Christophe Tholl and Ann Kiefer, the Homeschooling Mathematics , survey in Luxembourgish high-schools, 2021.

The articles (translated into Dutch by Luc van de Broek) appeared in the magazine Uitwiskeling.

- Article
*Trigonometry for the multiples of 3 degrees*, with Deborah Stranen. -
Article
*5-Con triangles*. -
Article
*The Art Gallery Problem*. -
Article
*The 15-puzzle*. -
Article
*Four points, two distances*. -
Article
*The seven bridges of Königsberg*. -
Article
*Discover multisets*. -
Article
*The ABCD of cyclic quadrilaterals*, with Engjëll Begalla. -
Article
*Every number is the beginning of a power of 2*. -
Article
*Staircase numbers*.