Problem: Yohaku: A new type of number puzzle for students

Author: Mike Jacobs
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This article explores number sense problem solving using Yohaku puzzles. Each month, elementary school teachers are presented with a problem along with suggested instructional notes; asked to use the problem in their own classrooms; and encouraged to report solutions, strategies, reflections, and misconceptions to the journal audience.

Contributor Notes

Mike Jacobs,, is a K–grade 12 mathematics consultant for Durham Catholic District School Board in Ontario, Canada. Originally from Yorkshire in the United Kingdom, he has been teaching for twenty-seven years. He has created Yohaku puzzles as a means of both encouraging problem solving as well as practicing and improving number sense.

Edited by Cathy Marks Krpan,, a professor at the Ontario Institute for Studies in Education at the University of Toronto, Canada. She teaches math education courses in the Department of Curriculum and Teaching graduate program. Each month, this section of the Problem Solvers department features a new challenge for students. Readers are encouraged to submit problems to be considered for future columns. Receipt of problems will not be acknowledged; however, those selected for publication will be credited to the author. Find submission guidelines for all departments at

(Corresponding author is Jacobs
(Corresponding author is Krpan
Teaching Children Mathematics
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