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Triangle ABC is isosceles with AB = BC. If AC = 20 and [ABC] = 240, then find the perimeter of triangle ABC.

Hello! I have this problem for a math class and I'm a bit confused. What do the brackets around ABC mean? Please don't tell me the answer, as I'd like to figure it out myself. :) I've tried searching it up, but it's a bit confusing. Thank in advance for your help! 

 Jun 21, 2020
 #1
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Hi.

 

[ABC] is the area of ABC.

 Jun 21, 2020
edited by hugomimihu  Jun 21, 2020
 #2
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Oh haha thank you! That makes a lot more sense now! 

Guest Jun 21, 2020
 #3
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np lol

hugomimihu  Jun 21, 2020
 #4
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Sorry for bothering you again! Should I split the triangle in half, and use pythagorean therom? If so how do I found out the height? 

Guest Jun 21, 2020
 #5
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hi, sorry for the late reply.

 

Anyways!

 

We know that AC is the base. 

 

The formula for area of ABC is, lh/2, so l*h = 480.

 

We also know that AC is the l.

 

Can you tell the height now?

 

Then, use the height, and using pythog, calculate the sides.

 

(only one is required as it's Isoceles, and remember that the base needs to be divided by two to do the pythog!)

hugomimihu  Jun 21, 2020
 #6
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Does that mean the height would be 120?

haha, i must seem really dumb right now. excuse my stupidity. 

Guest Jun 21, 2020
 #10
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haha nvm idk where i got that from

Guest Jun 21, 2020
 #11
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thank you so much for all your help!

Guest Jun 21, 2020
 #12
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Again, apologies for my late reply.

I sssume you figured it out, and if so, great job, if not, feel free to ask here!

hugomimihu  Jun 21, 2020

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