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Current time:0:00Total duration:4:04

Identifying scale copies

CCSS.Math:

Video transcript

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 so 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 so there's multiple ways that you could approach this one ways to say well let's see what the scaling factor would be so we can look at the length side lengths so this side right over here it has length three on figure a this side length right over here has length 1 2 3 4 5 this side length has length 5 as well this has length 5 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 so to go from this side if we scale up the corresponding side 2 that would be this side right over here and what is its length well its length when you scale it up looks like 5 so to go from 3 to 5 you would have to multiply by 5/3 5/3 but let's look at this side now so it's 5 in Figure a what length is it in Figure B well it is 1 2 3 4 5 it's still 5 so to go from 5 to 5 you have to multiply by 1 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 so in this example is Figure B a scaled version of figure a pause the video and see if you can figure it out alright we're going to do the same exercise and here they've given us the measures of the different sides so this side has length 2 this side has length the corresponding side or what could be the corresponding side has length 6 to go from 2 to 6 you have to multiply by 3 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 has length fourteen well here we're not multiplying by three if these were scaled a figure B was a scaled up version of figure a we would multiply by three but six times three is not fourteen it's 18 so these actually are not figure B is not a scaled version of figure a let's do one more example so once again pause this video and see if figure B is a scaled version of figure a so we're do the same exercise let's look at potentially corresponding sides so that side to that side to go from 4 to 12 we would multiply by 3 and then we could look at this side and this side to go from 4 to 12 once again you multiply by 3 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 4 to 12 multiplying by 3 looks good so far and then we could look at this side and this side 2 point 2 to 6 point 6 once again multiplying by 3 looking really good and then we only have one last one to check two point two to six point six 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