Multiplying Negative Numbers with Rectangles

I love using rectangles as a model for multiplication. In this video, Mike & son offer a pithy demonstration of WHY a negative number times a negative number has to come out positive:


Tabletop Academy PressGet monthly math tips and activity ideas, and be the first to hear about new books, revisions, and sales or other promotions. Sign up for my Tabletop Academy Press Updates email list.


4 thoughts on “Multiplying Negative Numbers with Rectangles”

  1. James Tanton has a video that does the same thing on a whiteboard, just drawing the rectangles, but I think it’s even more magical to see it acted out with the blocks.

  2. That’s really neat! Really shows why in this case minus X minus has to be a plus.

    I must use manipulatives to represent the grid method for multiplication in class!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s