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Exploring scale copies

Sal uses virtual manipulatives to identify figures that scale proportionally.

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Video transcript

- [Instructor] We are told, "Drag the sliders." And then they say, "Which slider creates a scale "copy of the shape?" Or, "Which slider creates scale copies of the shape?" So let's just see and explore this a little bit. Okay, that's pretty neat, these sliders seem to change the shape in some way, and in different ways. So shape B right over here, so it starts off, it looks like the width is a little bit bigger than the height, I'm just trying to eyeball it, we don't know the exact numbers. And so in order to create a scaled copy, you'd want to scale the width, you'd want to scale this bottom side, and the top side, and all of the sides. You'd want to scale by the same factor. But as we move this slider, it seems like it's only scaling the width, it's not scaling the height. So this slider, shape B right over here, the slider for shape B is not creating scale copies of itself, it's only increasing the width, not the height. While shape A, it looks like it is increasing both the width and the height, so that would be a scale copy. So for example, that looks like a scale copy of this, which looks like a scale copy of this, which looks like a scale copy of that, which was our original shape. That is not a scaled copy of this. Let's do another example. So once again they say, "Drag the sliders." And they say, "Which slider creates a scale copy "of the shape?" All right, let's get shape A. So this does look like we're scaling down, but we're scaling both the width and the height by the same factor, so this shape A slider does look like it's creating scale copies of the shape. B right over here, well now we're only scaling, it looks like we're only scaling the height, but not the width, so this is not creating scale copies of our original shape. It's elongating it, it's increasing its height, but not the width.