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ACT Math: Plane Geometry Drill 3, Problem 1. What is the area of the trapezoid shape in the video?
ACT Math Pre-Algebra Drill 2, Problem 5. Given the chart in the video, what is the mode?
What is the Perimeter of Triangle GHF? 328 Views
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Description:
ACT Math: Plane Geometry Drill 2, Problem 2. What is the perimeter of triangle GHF?
Transcript
- 00:02
Here's your shmoop du jour: What is the perimeter of triangle GHF?
- 00:07
And here are the potential answers...
- 00:12
First let's be clear that it's THIS triangle we're talking about -- so....why would
- 00:16
the question SHOW us all this other stuff?
- 00:18
Hm...
Full Transcript
- 00:19
Yeah. Well -- FGH and FDE are SIMILAR triangles -- that is, all their angles are equal, and
- 00:25
GH is parallel to DE.
- 00:26
How do we know? Well, since the two triangles are SIMILAR, it means that the perimeter edges
- 00:27
must parallel.
- 00:27
Start by finding the perimeter of triangle FDE...
- 00:30
We get 8 plus 2 plus 6 plus 2 plus 8... which is 26.
- 00:35
We want to find GH and we know that GH is proportional to DE.
- 00:40
So we can write FG is to FD, or 8 is to 10, as GH is to DE -- and DE is 6... so we get
- 00:44
the ratio 8 is to 10 as GH is to 6.
- 00:47
Cross-multiply and we get 48 equals 10 times GH... so the distance GH is 48 over 10...
- 00:55
or 4.8.
- 00:56
Now we have to just add the perimeter sides of 8 and 8 which is 16; add to 4.8 and we
- 01:04
get 20.8 as the perimeter for triangle GHF.
- 01:07
Answer D.
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