North School Maths - Geeking out on subtraction

8/3/2019

After listening to the podcast of John Spencer (The Creative Classroom: http://www.spencerauthor.com/critical-consuming/) I was inspired by the term ‘Geeking out’

Musicians love listening to music
Fashion designs are always looked at other peoples outfits!
Writers love to read books!
Chefs love eating!
Sports stars love watching games.

In every profession, people ‘geek out’ in order to become better. When you love something, you consume as much material about it as you can. Our goal is to ‘geek out’ on subtraction. How much can we learn? What methods are the most efficient? What are the hidden details that most people miss or don’t get? What are the similarities between different methods?

In 5/6 PSS, we ‘Geeked out’ on subtraction. The best part was sharing our ideas and trialling new methods.

The objective for this task was to have students critically analyse subtraction misconceptions. Eg. Not knowing how to rename, thinking 3 – 6 is 0 because ‘you’ve run out’. The students were to identify the mistake and switch from learner to teacher to explain to others what to do next.

This diagram is the end result of the discussion with my class about what they thought the mathematician had done. The discussion we had was much clearer than my attempts to record it quickly (but during the discussion, my writing made perfect sense). What it highlights is that it was fairly easy for them to articulate what was wrong, but they found it challenging to give reasons for why they thought the learner had made that mistake and how they could help them.

The terms renaming thingo and switcharooni were part of the discussion rather than any sourced strategies.

The follow up to this lesson was for students to critically consume as many subtraction strategies as possible. This meant exploring, trialling, reflecting and comparing.