Question

If the area of triangle DEF is 220.5 cm^2, what is the area of triangle ABC?

Answer 1

ABC~DEF

Answer 2

from the triangle DEF you know its area and base then you can find the height

Answer 3

h=2*220.5/21
=441/21
=21

Answer 4

yes but no need

Answer 5

for two similiar triangles, ratio of areas = ratio of sides squared

Answer 6

25/49?

Answer 7

You there @caozeyuan

Answer 8

@MaryLovell15 Still need help with it?

Answer 9

Yes! :( @JonnyVonny

Answer 10

Mmk, so, you found the height of one triangle, and you know its base.

Answer 11

Right.

Answer 12

So, the height and base are both 21?...

Answer 13

Yup, which, some triangles are like that. They are called equilateral triangles; the sides and angles are all the same.

Answer 14

So, you have the height and base, and you know they're similar, so you can set up a ratio between the two:

Answer 15

height 21 x height
base 21 15 height

Answer 16

Are you following me? Or are you confused?

Answer 17

I understand so far.

Answer 18

So, now that we have those ratios, we can cross multiply and solve for x. Tell me what you get and I'll tell you what I got.

Answer 19

x=15

Answer 20

@JonnyVonny

Answer 21

Yes, that is what i got aswell

Answer 22

So the area is 112.5?

Answer 23

So, now, just get the area via:
A=.5b*h

Answer 24

Yup, well, thats what we both got, at least.

Answer 25

There shouldn't be a reason why its wrong. Math does have a way at getting at you, however.:b

Answer 26

I honestly don't care if it's wrong at this point. Lol, I've been stuck on this for awhile.

Answer 27

Lol, I was just playing around; this is the way you're suppose to do it; find comparable numbers, then cross multiply. Know this process; you'll be using it a lot.

Answer 28

Thanks for your help!