KenKen
In the English-language KenKen books of Will Shortz, the issue of the non-associativity of division and subtraction is addressed by restricting clues based on either of those operations to cages of only two cells in which the numbers may appear in any order.
In 2007, toy inventor Robert Fuhrer, owner of Nextoy and creator of Gator Golf, Crocodile Dentist, and dozens of other popular toys and games, encountered KenKen books published in Japan by the educational publisher Gakken Co., Ltd. and titled "Kashikoku naru Puzzle" (賢くなるパズル, Kashikoku naru pazuru, lit.
[2] Fuhrer's company Nextoy, LLC (now holder of a trademark on "KenKen" and "KenDoku" as a name for brain-training puzzles) and chess International Master David Levy helped bring the puzzles to the attention of Michael Harvey, an editor of The Times (London).
[5] Harvey, impressed with what he calls its "depth and magnitude", arranged for publication of such puzzles, starting in March 2008, in The Times.
[8] The magazine, which is one of Europe's largest news publications, offers KenKen puzzles on their mobile app.
[9] KenKen is also being used by over 30,000 teachers throughout the United States to teach math skills, problem solving techniques, logic, and critical thinking.
In the example here: (sets of numbers such as "5,6" and "4,5" could appear in any order) More complex KenKen problems are formed using the principles described above but omitting the symbols +, −, × and ÷, thus leaving them as yet another unknown to be determined.
KenKen has collaborated with the National Council of Teachers of Mathematics (NCTM), to create a mobile app in order to help students develop their math and logic skills.
In 2016, five students in India, Gaurav Pandey, Neharika Rajesh, Visharad Srivastava, Devika Pillai and Kajal Agarwal, beat 75,000 competitors to secure a place in the International Round that was held in New York on 18th Dec 2016.
[19] Over the past several years KenKen has expanded internationally and now runs national tournaments in multiple countries for students.
