The Triangleman Decimal Institute [TDI]

In recent weeks, I have written several times about decimals and their treatment in curriculum. In discussions surrounding that writing, it has become clear to me that everyone involved in children’s learning of decimals can both learn and contribute to the learning of others.


Which is why I am excited to announce…

The Triangleman Decimal Institute

For seven weeks, starting Monday, September 30, I will invite all interested parties to an online conversation about decimals and learning decimals.

Each Monday, I’ll have a new post here to launch and focus our discussions. Comments will be closed in order to move the discussions to more productive venues (see below).

You may participate in any way that you like, including the following:

  1. Self study. Read at your leisure. Discuss with yourself, your colleagues, your spouse and/or your Australian Labradoodle.
  2. Twitter. I invite you to use the #decimalchat hashtag to respond, argue, offer evidence and discuss.
  3. Canvas. It is no secret that I love this LMS. I have established a course in Canvas. The course is public, free and you may self-enroll. We will mainly use the discussion forums there, which function MUCH better than WordPress comments for our purposes. I will establish a new discussion forum there for each week’s post, but students (i.e. you) can also create discussions.

You may come and go as you please.

My promise to you is to keep myself on the schedule in the syllabus below and to engage to the extent possible in the discussions on Twitter and Canvas.


Come join us for some or all of the following.

Week 1 (Sept. 30): Decimals before fractions?

Week 2 (Oct. 7): Money and decimals.

Week 3 (Oct. 14): Children’s experiences with partitioning.

Week 4 (Oct. 21): Interlude on the slicing of pizzas.

Week 5 (Oct. 28): Grouping is different from partitioning.

Week 6 (Nov. 4): Decimals and curriculum (Common Core).

Week 7 (Nov. 14): Summary and wrap up.

There will be no grades, tests or tuition. Just the love of knowledge and the collective passion of teachers wanting to do their best.

See you in class on Monday!

Note from Canvas:

This course has enabled open enrollment. Students can self-enroll in the course once you share with them this URL: Alternatively, they can sign up at  and use the following join code: MY4YM3


11 responses to “The Triangleman Decimal Institute [TDI]

  1. Sounds interesting! I’ve signed up, though I’m busy enough with other things that I may not be more than a lurker.

  2. I tweeted “I’M IN!” even before I noticed the bit about discussing this with your Australian Labradoodle. I should have mentioned that Topper, my Australian Labradoodle, is also in!!!

    – Elizabeth (@cheesemonkeysf)

  3. oh my gosh. week 4’s title is so perfect. i love that you are doing this!

  4. Pingback: Parents, Teachers: Learn about Teaching Decimals | Let's Play Math!

  5. Pingback: Money and decimals [TDI 2] | Overthinking my teaching

  6. Pingback: Reflections on teaching | Overthinking my teaching

  7. Pingback: On the slicing of pizzas [TDI 4] | Overthinking my teaching

  8. Pingback: Grouping is different from partitioning [TDI 5] | Overthinking my teaching

  9. Pingback: Decimals and curriculum (Common Core) [TDI 6] | Overthinking my teaching

  10. Pingback: Summary and wrap up [TDI 7] | Overthinking my teaching

  11. Pingback: Wiggins question #4 | Overthinking my teaching

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