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Geometry Videos 51 videos

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SAT Math 10.4 Geometry and Measurement 380 Views


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Description:

SAT Math 10.4 Geometry and Measurement. What is the perimeter of triangle DEF?

Language:
English Language

Transcript

00:02

Here’s your shmoop du jour, brought to you by similar triangles.

00:07

If it wasn’t for the tattoo, we wouldn’t be able to tell them apart.

00:10

Triangle ABC is similar to triangle DEF. What is the perimeter of triangle DEF?

00:18

Okay, we’ve got a couple of similar triangles here.

00:21

Apparently triangles of a feather flock together...

00:24

All right, so these are both right triangles…

00:26

…and one of them has a leg with length 6 and a hypotenuse with length 10…

00:31

…Hello! Looks like we’ve got a 3-4-5 triangle...

00:35

Both known distances have been doubled from the original 3-4-5 ratio…

00:39

…so we know we have to double the missing length as well.

00:43

Four times two is eight… and we have a triangle with sides of 6, 8 and 10.

00:50

Plugging those numbers into our internal adding machine… we get a total perimeter of 24.

00:55

Now, before you waste gobs of time trying to figure out what the lengths of the sides in our other triangle are…

01:01

…just note that the one side we DO know is 2/3 of the corresponding side in triangle number one.

01:07

These triangles are similar… so the perimeter is going to carry over the same ratio.

01:12

We’ll take 24 times 2/3… to get 16…and that’s our answer. We're done!

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