Ron is an Associate Professor, Teaching Stream, Emeritus at the University of Toronto where he taught mathematics courses for pre-service middle and high school teachers for 17 years. Before joining the faculty of the University of Toronto, Ron taught middle and high school mathematics for 23 years in coed public schools and a K-12 all-girls school.

Ron's professional activities include consultations for international, private and public schools; technology companies, museums and public broadcasters.

Ron has been a presenter at hundreds of conferences, including the highly-regarded Anja S. Greer Conference on Mathematics and Technology at Phillips Exeter Academy for 29 years in a row; 63 National Council of Teachers of Mathematics (NCTM) Annual and Regional Conferences; 39 consecutive Ontario Association for Mathematics Education Annual Conferences and 12 East Asia Regional Council of Overseas Schools Conferences and Weekend Workshops.

Ron has been a prolific author for the Mathematics Teacher, published by the National Council of Mathematics Teachers (The Mathematical Lens & Media Clips) and the Ontario Mathematics Gazette, published by the Ontario Association for Mathematics Education (Mathematical Snapshots). Ron was a member of the writing team for Principles and Standards for School Mathematics, published by the NCTM. He wrote mathematical activities, distributed by Words and Numbers, for high school students that were based on episodes of the prime time series NUMB3RS on CBS TV.

Ron loves coddiwompling and he sees mathematics everywhere he walks. He never leaves home without his pair of math glasses and camera so that he is always ready to snap photos of numbers, patterns, shapes, solids, curves and shadows. Throughout his career, Ron has made connections between the mathematics curriculum and daily life in an effort to help students appreciate and enjoy mathematics.

Ron is well known for his expertise in designing Math Trails. Ron has created these math paths in many locations around the world including Singapore, where thousands of students and hundreds of teachers have enjoyed his walks in Suntec City, Fort Canning Park and the NUS Art Museum. Ron has developed Math Trails in Manhattan for Math for America, the Avenues School and the Museum of Mathematics at many locations in the city.

Ron is the recipient of the 2015 Margaret Sinclair Memorial Award Recognizing Innovation and Excellence in Mathematics Education awarded by the Fields Institute.

In the diagram, the same four shapes have been used to make two congruent right-angled triangles. A hole has appeared in the bottom triangle which is of course impossible. Or is it? Explain what is going on here.