Question

looking from a distance, a girl standing in front of a tree appears to have the same height as the tree. if the girl has a height of 160cm and is standing 5m from the viewer, what is the height of the tree if it is 25m from the viewer?

Answer 1

what do they mean by thw ord "viewer"?

Answer 2

The "viewer" is somebody looking at a girl with a tree in the background.

And the answer is that it depends on where the viewer's eyes are.

If the viewer is a couple of inches taller than the girl so that his eyes are level with the top of the girl's head, then the tree is 160cm tall.

If the viewer is a midget and his eyes are 1 meter off the ground, then the tree will be 4 meters high.

Answer 3

Thanks!! :-)

Answer 4

but in this case the viewer is between the girl and the tree

Answer 5

am i right?

Answer 6

They usually show a picture with these. Is the viewer between them? Odd. Usually it is on the ground, or they have some other line, triangle, etc. to make it clear.

Answer 7

no they havent provided a picture. thats what i hate about it

Answer 8

Have you been studying similar triangles in this section?

Answer 9

you are right

Answer 10

i am

Answer 11

i wish if someone can draw it

Answer 12

Then I would personally assume they meant this to be a similar triangles problem and that they are giving you two sides of the triangles for you to the girl, and one side from you to the tree.

Answer 13

-"in this case the viewer is between the girl and the tree"

No, the girl is between the tree and the viewer.

The girl is 5m from the viewer and the tree is 25m from the viewer.

Answer 14

You being the viewer.

Answer 15

5m/160cm = 25m/x

Answer 16

so x=800cm = 8m

Answer 17

height of the tree is 8m

Answer 18

Generally you want things in uniform units to make sure there are no mistakes made by issues with the units.

Answer 19

?

Answer 20

But yah, looks like 8 for the first one. Someties changes in units cna really matter. Especially if a square is involved. So it is just better to get used to doing uniform units.

Answer 21

Or 8m for the tree... foirst one...there is only one. LOL

Answer 22

That assumes the viewer is like an ant, but since you have been doing similar triangles, it seems to be a safe assumption to make. Do you understand why the height of the viewer really changes things?

Answer 23

we dont know the height of the viewer. it isnt given to us

Answer 24

all we know is the height of the girl which is 160cm

Answer 25

Yes. I am just saying, why that would change things. Do you know?

Answer 26

let me think about it for a moment :)

Answer 27

do you mean height or length?

Answer 28

The height of the viewer. What it does to the entire problem.

Answer 29

i dont know. can you please tell me?

Answer 30

if the viewer is short the length of the tree would shorten too

Answer 31

Not quite. I am working on showing. hehe.

Answer 32

cheers

Answer 33

The red line is a viewer that is half the size of the girl, but the green is like an ant.

Answer 34

That is what qweqwe123123123123111 was talking about and why I had to say we assume they mean similar triangles. OK?

Answer 35

so the ant would see the tree much more higher if only the ant had brains :)

Answer 36

Hey, the ant's might just have a hive mind and take over the planet, one giant step for man is lots of tiny ones for ant-kind!

Answer 37

lol

Answer 38

so from the picture i can see that there are two similar triangles

Answer 39

We assumed the ant case, and the ant to girl is 5m and ant to tree is 25m. We did this because they gave us the full height of the girl. If they had said half the height of the girl, we would assume the viewer was at half the height of the girl.

Answer 40

i have another problem which involves similar triangles

Answer 41

but i need to draw the diagram

Answer 42

Well, draw it and try it and then post what you get and lots of people here will be happy to check it. If you get stuck, post how far you got.

Answer 43

i did try but my answers were incorrect

Answer 44

Well, post up what you got and how. Hard to fix things if you don't show us them. If you do, we can target the real issue.

Answer 45

sweet i will right now