The Rounding Pandemic (2014)

[ColinWright]

https://cavmaths.wordpress.com/2014/02/10/the-rounding-pandemic/

[jonsen]

Are there any other areas of maths being taught wrong on this sort of scale?

An online video course could be some scale.

I once saw a video lesson on the Pythagorean theorem: Drawing a right-angled triangle, marking the hypothenuse with the letter h, marking both of the catheti with the letter c, then proceeds to write the formula

  h^2 = c^2 + c^2