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That “triangle thing”

September 12, 2018

Today grade 9s worked on remembering a lot about area and perimeter calculations for complex shapes.  

This particular question could be worked in a few ways.  Some saw a big rectangle with a square and triangle removed, while others broke it into rectangles and triangles.


We saw another approach involves a trapezoid (and our new favourite song…to the tune of Frère Jacques)

L’aire d’un trapèze, l’aire d’un trapèze

Base plus base, base plus base

Divisée par deux, divisée par deux

Fois hauteur, fois hauteur.


To calculate the perimeter we needed to figure out the missing side length, which caused many people to try to remember that triangle thing (a.k.a. Pythagorean theorem).

To help remind us of how it works we watched a video

We’re going home to measure TV screens tonight (which are all sold based on their diagonal length).  We’ll tabulate results tomorrow.

Good work again grade 9s.

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