Dec 14, 2009
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sorry i can't draw the picture, but I guess you can solve this w/o picture as well.

Trangle ABC is similar to another triangle DEF. AB is 4 units long and DE is 8 units long. If ABC has area of 10 square units, what is the are af DEF in square units?

answer is 40,
 

herkulease

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Jan 23, 2009
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here's how I solved it. the key word is that they are similar. I'm guess its drawn similar too. Plus we are given the that AB is 4 and DE is 8. essentially double in size.

I'm guessing that one of the answer choices is 20?

Anyhow area of triangle is 0.5(bh)

for the ABC triangle we have the base AB as 4 and we know the area as 10.

plug in into the formula we get the height 5 for triangle ABC.

Given the information previously that triangle DEF is double in size to triangle ABC then the height of Triangle DEF is 10.

Now we plug that info into the formula. 0.5(8*10) = 40
 

dentalWorks

Nights Watchmen
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Jun 25, 2009
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Keyword here is "similar", as soon as I was done reading your problem, I made the assumption that Trangle DEF has lines that are twice as much as ABC's lines.

Find area of ABC
Okay, for ABC, lets find the area:
(1/2)(B)(h) = 10
(1/2)(4)(h) = 10....solving for h
h = 5 <-----this is the height of ABC, becuase the 2 triangles are "similar", I am going to say that the hight of DEF = 10

Find area of DEF
(1/2)(B)(h) = DEF area
(1/2)(8)(10) = DEF area
40 = DEF area