How the Sign Rules Work, and Why

How to Not Suck at Math, Part 6

This is part of a new series about how to help yourself or your kids improve in mathematics. It’s based partly on my own experience of having to learn how to learn mathematics, partly on extensive tutoring experience, and partly on many conversations with homeschooling parents, as well as parents struggling to understand Common Core mathematics. Many future editions are already planned, but feel free to leave suggestions for future editions in the comments (open for paid subscribers) or by email to hollymathnerd at gmail dot com.

The first five posts are not behind the paywall; all future posts will be; this link will give you 10% off. If you’d like to get them but can’t afford a paid subscription, email me at hollymathnerd at gmail dot com and I’ll give you a free one

Previous posts in the series:

Part 1: Addition and Subtraction

Part 2: Multiplication, Division, and Fractions

Part 3: The Major Key of Mathematical Fluency

Part 4: A Proof for this Approach to Numeracy

Part 5: “I’m Just Not A Math Person!”

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Why The Sign Rules Work the Way They Do

Welcome back to my math series!

September was a busy month for me, math-wise. I am going to be applying to grad school in mathematics soon. (Online only programs; will continue to work full-time.) If anyone has an idea which of the internet’s 973 million GRE Practice Tests actually does a good job of approximating the GRE, please comment or email. Now on to part 6.

Negative Times Negative is Positive and Positive Times Negative Is Negative….But Why?

In previous posts, we’ve covered addition, subtraction, multiplication, and division, as well as the importance of the Fundamental Theorem of Arithmetic, which teaches us that prime numbers are the building blocks of everything. I also made a short detour into cultural commentary, lamenting the widespread notion that it’s ok to just declare yourself “not a math person” and stop trying for mathematical literacy.

Today we’re going to talk about negative numbers and how and why the sign rules work.