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## Basic geometry and measurement

### Course: Basic geometry and measurement > Unit 12

Lesson 1: Scale copies- Identifying corresponding parts of scaled copies
- Corresponding points and sides of scaled shapes
- Corresponding sides and points
- Identifying scale copies
- Identify scale copies
- Identifying scale factor in drawings
- Identify scale factor in scale drawings
- Identifying values in scale copies
- Scale copies

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# Identifying scale copies

Sal looks at side measures on figures to determine if they are scale copies.

## Want to join the conversation?

- how can we actually calculate the scale copy of one figure to the other figure?

Any answers or comments will be helpful.

Thanks to people who help to answer this question.

#patient for answer#(16 votes)- Eunice, first you have to look at one of the sides of the scaled copy. If they are divisible by the numbers in the original shape, then try and see if the others sides of the scaled copy are scaled by the same factor. If they are, then they are a scaled copy. Hope this helped!(20 votes)

- i like cheeseburgers and french fries(16 votes)
- Hello awesome people! This is just a message to let you know that you're doing awesome! Don't push yourself too hard! If you're trying, that's all that matters! Make sure you take your meds, take a break, drink some water, eat some healthy food, and if you're feeling like it, exercise a little! You are loved so much and if you ever need to talk my scratch username is cinnqmorrol. Love you, bye!(12 votes)
- on your practice can you make the lines for the squares more visable, it is kind of hard to see.(5 votes)
- I don’t think he can do that. He would have to change the code for the exercises which he cannot do(2 votes)

- How would we do this with 3D shapes instead of 2D?(7 votes)
- what is a scale copy? Help me plz.(0 votes)
- A scale copy of a figure is a figure that is geometrically similar to the original figure.

This means that the scale copy and the original figure have the same shape but possibly different sizes.

More precisely, the angles of the scale copy are equal to the corresponding angles of the original figure, and the ratio of the side lengths of the scale copy is the same as the ratio of the corresponding side lengths of the original figure.

In real life, a scale copy is often smaller than the original figure. For example, the drawing of a floor plan for a room is a scale copy of the actual floor of the room. The floor plan drawing has the same shape as but is smaller than the actual floor. For example, if the actual floor is a rectangle measuring 12 feet by 16 feet, a scale copy could be a drawing of a 6-inch by 8-inch rectangle (because 12ft:16ft is the same ratio as 6in:8in).(14 votes)

- Guys im in 3rd grade lol(5 votes)
- Why do we live we love we lie? Also uwu(5 votes)

## Video transcript

- [Instructor] What we're
going to do in this video is look at pairs of figures, and see if they are scaled
copies of each other. For example, in this diagram, is Figure B a scaled version of Figure A? Pause the video and see if
you can figure that out. There's multiple ways that
you could approach this. One way is to say, "Well, let's see what the
scaling factor would be." We could look at the side lengths. This side right over here
has length three on Figure A. This side length right over here has length one, two, three, four, five. This side length has length five as well. This has length five. This length, we could figure it out with the Pythagorean Theorem, but I won't even look
at that one just yet. But let's look at corresponding sides. To go from this side. If we scale up, the
corresponding side to that would be this side right over here. What is its length? Well, its length, when you
scale it up, looks like five. So to go from three to five you would have to multiply by 5/3. 5/3. But let's look at this side now. It's five in Figure A. What length is it in Figure B? Well, it is one, two, three, four, five. It's still five, so to
go from five to five, you have to multiply it by one, and so you have a different scaling factor for corresponding, or what could have been
corresponding sides. This side right over here,
you're scaling up by 5/3, while this bottom side,
this base right here, you're not scaling at all. So these actually are not
scaled versions of each other. Let's do another example. In this example, is Figure B
a scaled version of Figure A? Pause the video and see
if you can figure it out. All right, well we're
gonna do the same exercise, and here they've given us the measures of the different sides. This side has length two. This side has length the corresponding side, or what could be the
corresponding side has length six. To go from two to six, you
have to multiply by three. If we look at these two
potentially corresponding sides, that side and that side, once again, to go from four to twelve,
you would multiply by three, so that is looking good as well. Now to go from this side down
here, this has length six. The potentially corresponding
side right over here has the length 14. Well here we're not multiplying by three. If these were scaled If Figure B was a scaled-up
version of Figure A, we would multiply by three, but six times three is not 14, it's 18, so these actually are not Figure B is not a scaled
version of Figure A. Let's do one more example. Once again, pause this video and see if Figure B is a
scaled version of Figure A. We're gonna do the same exercise. Let's look at potentially
corresponding sides. That side to that side, to go from four to 12, we would multiply by three, and then we could look at
this side and this side, to go from four to 12, once
again you multiply by three, so that's looking good so far. We could look at this side and this side, potentially corresponding sides. Once again, we're going from four to 12, multiplying by three. Looks good so far. And then we could look at
this side and this side. 2.2 to 6.6, once again
multiplying by three. Looking really good. And then we only have
one last one to check. 2.2 to 6.6, once again
multiplying by three, so all of the side lengths
have been scaled up by three, so we can feel pretty good that Figure B is indeed a scaled-up
representation of Figure A.