14 January 2023: I presented “Geometric Puzzles: Tiles and Rep-Tiles” at the San Francisco Math Teachers’ Circle. More info on my Talks page.

5 December 2022: I sent out my e-newsletter: in defense of algebra, basics of classroom management, course evaluations, eclecticism, and more. Subscribe!

27 November 2022: I restored the graphics for Unexpected Ratio.

17 September 2022: I presented “Geometric Puzzles for All Ages” at the Florida Math Circles Network online conference. Handout, with lots of links.

18 August 2022: I sent out my e-newsletter, with links to recent blog posts and new material on my website. Subscribe!

31 May 2022: I helped script an animation for TED-Ed, The Fortress Riddle. It’s a version of the McNuggets problem, and I don’t like this version enough to embed it on my site. Instead, I recommend the Algebra: Themes, Tools, Concepts version (Building Block Numbers), or this full lesson plan I created with Amanda Cangelosi. See also my letter to Mathematics Teacher with a compact presentation of a generalization.

27 April 2022: I sent out my e-newsletter, with links to recent blog posts and new material on my website.

26 April 2022: I scripted an animation for TED-Ed, A Vampire Riddle. I embedded the video in my new Slumber Theory page.

29 March 2022: I scripted an animation for TED-Ed, A Riddle of Ice and Fire. I embedded the video in my Map Coloring page.

19 January 2022: I sent out my e-newsletter, which included many links — recent blog posts, recent additions and updates to my website, and popular pages according to Google.

4 December 2021: I presented a hands-on workshop at the California Math Council conference in Asilomar — Tiling: a Springboard for Geometry. Tiling the plane (tessellation) provides opportunities for students to do creative work they take pride in. It connects with art (e.g. Escher) and culture (e.g. Islamic design). And it provides a rich context for basic geometry (sum of the angles in a polygon, parallels and transversals, regular polygons, etc.) and transformational geometry (rigid motions and some theorems about them).

16 September 2021: I sent out my e-newsletter, which included links to recent blog posts and numerous new and improved pages on my website.

2-6 August 2021: With Rachel Chou, I presented a hybrid workshop — No Limits! for teachers of Algebra 2, Trigonometry, and Precalculus. Hosted by Menlo School.

19-23 July 2021: I will present an online workshop on “Symmetry: A Unifying Thread Across Grades and Cultures”. The Symmetry workshop has been canceled.

June 2021: My arithmetic games are currently unavailable on the Snap! website. A GeoGebra version is on my website: Signed Numbers, Complex Numbers.

7 April 2021: I sent out my e-newsletter, which included links to my recent blog posts (Seeing is Believing?, and Fraction Rectangles, and to the new Pentomino Puzzle Books page on my website. I also used the newsletter to promote my summer workshop.

March 2021: My arithmetic games (Signed Numbers, Complex Numbers) now load fast from the Snap! website. (My design, programmed by Parisa Safa.)

11-12 Mar 2021 (4pm to 4pm Pacific Time): I participated in the Julia Robinson Math Festival’s Math Buffet, an international 24-hour online event for kids (and adults).

23 Feb 2021: I sent out my e-newsletter, which included links to my recent Tiling and Transformational Geometry blog posts, and to the new Symmetry home page on my website.

9 Feb 2021: Math Teachers’ Circle: Tangrams and Pentominoes are geometric puzzles which are fun and interesting for all ages. Can students use these manipulatives in an age of remote instruction? Yes! In this workshop, I shared virtual tools I created to make that possible. I proposed problems suitable for ages 9-99, and participants worked as a team to generate dozens of solutions. The activities touched on symmetry, area, congruence, and similarity.

6 Dec 2020: I presented “Symmetry: a unifying thread across grades and cultures” at the California Math Council-North virtual conference. We explored line and rotational symmetry with activities on free online platforms. We analyzed examples from all over the world. Bonus: links to online symmetry projects, as well as hands-on activities using mirrors, pattern blocks, tangrams, pentominoes, templates, and special papers for when you’re back in the classroom. (See my Talks page for info.)

2 Dec 2020: I restored the graphics in Math in the Long Period.

10 Nov 2020, 4:30-6:00pm PST: AC3ME and SFMTA (two Bay Area NCTM affiliates) hosted my workshop about some of my website’s free virtual manipulatives (Geoboard, Grid Paper, Lab Gear, Tiling, Pentominoes.) I showed how to use them, and suggested a problem for each one so that participants can practice then and there.

29 Sep 2020: I sent out my e-newsletter, which was largely focused on virtual manipulatives. I announced two upcoming online workshops: Nov 10, on virtual manipulatives (grades 6-12), and Dec 6 at the California Math Council North annual meeting) on symmetry.

17 June 2020: I sent out my e-newsletter. Topics included: “There is no one way”, a GeoGebra animations tutorial, sum and difference of cubes, Lab Gear graphics, symmetry, and my wallpapers catalog. Also: an announcement of my online summer / fall workshop — Hands-On Geometry.

15 June 2020: My July Hands-On Geometry summer workshop will happen online, assuming sufficient enrollment. The August iteration has been postponed to four Saturdays in September and October. I will be updating the summer / fall workshop page on my website as I get more information.

28 May 2020: I restored a post (Symmetry in Spain). Math-relevant photos, and links to photos, from a vacation in 2013.

10 February 2020: I sent out my e-newsletter. Topics included guided inquiry, conic sections, a polyomino puzzle, a grid approach to fractions, graphing ax+by=c, and number pyramids. Also: an announcement of my summer workshop — Hands-On Geometry on both coasts. Alas, there was a wrong date for the latter, and a couple of broken links. It’s all fixed online!

4 February 2020: Infinity is a mind-bending topic that everyone finds interesting. I shared infinity paradoxes, puzzles, problems, and proofs from a high school course I developed at the Berkeley Math Teachers’ Circle.

7 December 2019: At the Asilomar conference, Kim Seashore and I presented Lessons from Lew. (Kinesthetic angles, Golden Ratio, Symmetric Polygons.) Later, I presented Connect the Dots, an extravaganza of geoboard / dot paper activities for ages 9 to 99: curricular challenges, interesting puzzles, and some unsolved problems.

26 November 2019: I restored the graphics in my post Completing the Square.

30 October: I sent out my e-newsletter. The main topics were test retakes and a response to Freakonomics Radio episode about math education. I also highlighted recent contributions to my blog and website by Rachel Chou.

5 October 2019: Along with Kim Seashore, I was a presenter at Lessons from Lew, a free professional development session. We shared Lew Douglas’s lessons on angles, the golden ratio, symmetric polygons, and more. Links to an expanded version of the handouts, here.

18 September 2019: I added a link to Chris Bolognese’s Desmos Activity Builder version of Add Till It’s Plaid, a lesson plan on solving systems of linear equations.

12 September 2019: I restored the graphics in my post Add Till It’s Plaid, wherein I share a great lesson on solving systems of linear equations.

10 September 2019: I restored the graphics in my post Making a Vector in Desmos.

23 August 2019: I sent out my e-newsletter. The main topics were: “Taking Notes vs. Doing Math”; a review of a book that was a big influence on my teaching; the place of puzzles in math education. Plus a lot more. Subscribe!

17 August 2019: An entire post (about Doctor Dimension, the flat scientist) was missing. I restored it.

5 July 2019: I fixed more broken links, this time in a series of posts in which I challenge the dogmatic stance of teachers who are overly stingy about offering hints to students who are stuck: About Hints, About Hints, the sequel, and Hints! The topic that will not die.

1 July 2019: I fixed broken links to I’ve Got a Problem!, the first of two posts about a time where I was in the student’s shoes, and I learned a lot from it.

18 June 2019: I restored the figure in Geometric Series, a blog post about a geometric way to visualize the case where the common ratio is less than 1.

18 April 2019: I restored the graphics and repaired the links in my 2011 notes from a meeting of Escape from the Textbook! a grassroots math teacher group that met for a few years in the Bay Area.
(Part 1: tools, backward design | Part 2: Miras | Part 3: habits of mind)

12 April 2019: I restored the graphics in the Partitions post.

3 April 2019: I restored the graphics in the Egyptian Fractions post.

15 March 2019: I sent my e-newsletter out. The main topics were story tables, an argument against the shrinking of geometry, a book review, geoboards + related topics, and the announcement of my summer workshops. Subscribe!

6 March 2019: I fixed a broken link to Puzzles for the Classroom in the post Puzzle Creation.

20 February 2019: I restored a missing equation from Pruning the Curriculum, a 2015 blog post where I suggested teaching fewer topics in more ways. I also fixed a link to the related Mapping Out a Course.

5 February 2019, 5pm: Geoboard Puzzles and Problems. I led the East Bay Math Teachers’ Circle at Berkeley High. The geoboard is a great learning environment, but in this session we used it as an arena for puzzles and problems, some of them unsolved, involving diagonals, triangles, non-triangles, and zigzags! You can download the handout.

25 January 2019: I sent my e-newsletter out. The main topics were learning tools, and the announcement of my summer workshops. Subscribe!

14 January 2019: I restored five posts about the geoboard: Geoboard Triangles, No Three on a Line, Heilbronn’s Triangle, Ariadne’s String, and Geoboard Problems for Teachers.

9 January 2019: I will offer a grades 6-9 version of my workshop on Visual Algebra twice this summer: June 25-27 at Synapse School in Silicon Valley, and again August 7-9 at Atrium School near Boston. More information.

9 January 2019: I restored the graphics in two posts: “A New Algebra” where I bragged about Robert Davis’s praise for my approach; and Geoboards and Dot Paper, where I introduced subsequent posts on using these tools as a microworld for problem solving, and bragged about having invented the “tilted squares” intro to the Pythagorean theorem decades ago.

8 January 2019: I restored the post Themed Courses?, where I discuss the question of whether courses with a theme are preferable to “hodgepodge” courses, whose topics range widely.

8 January 2019: I restored the graphics in two posts: Inscribing Geoboard Squares in Polyominoes, a fun puzzle; and my 2014 Asilomar Report, which included interesting material about warmups.

28 December 2018: I restored the post Tiling, aka Tessellation, where I summarized some sessions at Twitter Math Camp, and linked to the various tiling items on my Web site.

28 December 2018: I restored the illustration in the “Enrichment” post.

24 December 2018: I restored the posts Geometric Construction, Continued and Programming and Math Education.

24 December 2018: I restored the diagram in the Curriculum Model post. The figure was the subject of the post! Also: I restored the graphics in the Make These Designs post.

22 December 2018: I restored the Math for Equity post, where I reviewed an excellent book about “Railside” school, where teachers developed tremendously effective approaches to teaching untracked classes in a “wrong side of the tracks” school. Their work was studied by math education researchers at both Stanford and Berkeley.

22 December 2018: I restored the “themes, tools, concepts” map in the Proportional Relationships post. That diagram was the main point of the post, so I feel bad that a few dozen visitors to the page didn’t get to see it.

22 December 2018: I restored the Time and Tide post, where I link to and discuss my three (!) presentations at Asilomar (2016), and propose some strategies to slow things down in classroom discussion.

21 December 2018: I restored the graphics in the Algebra Manipulatives post, where I compare the Lab Gear with other models, and reply to a correspondent. Also the illustration in Straightedge and Compass.

17 December 2018: I restored the Geoboard Problems for Teachers post. Surprisingly to me, this was one of my most visited post ever.

15 December 2018: I restored my Polyarcs post, which had not survived the move to WordPress. Interesting discussion in the comments!

14 December 2018: I found the graphics from my Stumped by Euclidea blog post on the Internet Archive’s Wayback Machine! It was a bit of work to put them back into the post, but not as much work as recreating them! I’ll continue to work my way back through the posts to restore content lost in the move from Blogger.

1 December 2018: I attended the California Math Council Northern Section meeting in Asilomar. My presentation was about Reaching the Full Range of students in a heterogeneous class (i.e. any class). I put lots of links about this on my Talks page.

27 November 2018: I moved my blog into WordPress (here.) I thought the move had happened smoothly, but some graphics, and some entire posts, failed to materialize. Also, many links are broken. If you come across these problems, please notify me, indicating which post had the issue. Thanks!