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**emmakatecumbo****Member**- Registered: 2017-09-22
- Posts: 35

I need help on these few problems i got wrong. I put teachers comments down below.

8. Each set of numbers below represents the lengths of three line segments.

Which set represent line segments that could be connected to form a triangle? Give the reasoning or show your work to support your choice

A. (3, 5, 7)

B. (3, 4, 8)

C.(1, 4, 6)

D. (1, 3, 5)

E. (5, 6, 11)

F. (1, 10, 20)

9. Each set of numbers below represents the lengths of three line segments.

Which set represent line segments that could be connected to form a triangle? Give the reasoning or show your work to support your choice

A. (2, 2, 5)

B. (5, 4, 1)

C.(5, 10, 15)

D. (7, 10, 16)

E. (2, 3, 5)

F. (5, 10, 25)

19. Here are two triangles. I am trying to measure the area of triangle ABC. The formula for area of a triangle is

base*height/2.

I know the base, but I need to find the height. I know the top of triangle ABC is directly above a point 4.5 units from point A. I also know that

What is the triangle's height? 19.31 square units

20. The sun is shining and I am on a hill. I want to measure the height of a tree downhill from me, using my one-meter stick, and a tape measure for measuring shadows. What do I do to take the slope of the hill into account? Not possible

Teacher Comments on work :

#8-9 incorrect... what is the RULE?

#19 this is the AREA... use it to find the HEIGHT... show all work

#20 this is just asking if you need to do anything special to take slope into account when you and the tree are on the SAME hill

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Hi emmakatecumbo,

Let's start with the first question. In any triangle, the sum of any two sides must be longer than the third side. (This is called the **triangle inequality**.)

For example, (3,5,7) can be a triangle, because:

3 + 5 > 7

3 + 7 > 5

5 + 7 > 3

Can you do the rest?

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**emmakatecumbo****Member**- Registered: 2017-09-22
- Posts: 35

So number 9 would be D.

7 + 10 > 16

10 + 16 > 7

16 + 7 > 10

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Correct! How about the others?

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**emmakatecumbo****Member**- Registered: 2017-09-22
- Posts: 35

I don't know how to do number 19. and 20

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It looks like you are missing part of the question for #19.

**LearnMathsFree: Videos on various topics.New: Integration Problem | Adding FractionsPopular: Continued Fractions | Metric Spaces | Duality**

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**Monox D. I-Fly****Member**- From: Indonesia
- Registered: 2015-12-02
- Posts: 1,334

I was scavenging old questions and found the question #20. Wanna put it in the student worksheet I make but I have no idea what is the correct answer. What is it?

Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away. May his adventurous soul rest in peace at heaven.

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**ganesh****Administrator**- Registered: 2005-06-28
- Posts: 26,826

Hi Monox D. I-Fly,

Searched for the problem and solution.

*The sun is shining and I am on a hill. I want to measure the height of a tree downhill from me, using my one-meter stick, and a tape measure for measuring shadows. What do I do to take the slope of the hill into account?A. Bend the meter stick. B. Place the meter stick on the hill. C. Call your mother. D. Using the meter stick and the tape measure, recreate the slope E. It's not possible. F. You don't need to do anything different so long as your meter stick is on the same slope as the tree.*

F is almost right, and is the nearest thing to a correct answer. What would make it correct would be the restriction that the two shadows, i.e. from the meterstick and the tree must be wholly contained in the slope. That is to say that your calculations will be off somewhat if the shadow of the tree reaches beyond the base of the hill and extends onto the presumably horizontal surface of the valley beneath the hill.

.It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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**Monox D. I-Fly****Member**- From: Indonesia
- Registered: 2015-12-02
- Posts: 1,334

Ah, thank you very much, ganesh!

Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away. May his adventurous soul rest in peace at heaven.

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**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,452

Hi Monox D. I-Fly,

If you stand close to the tree and stand the stick so that it mimics the 'lean' of the tree (if necessary as the tree may not be vertical) and not in the tree's shadow, then the tree and its shadow and the stick and its shadow make similar triangles. So, by measuring the two shadows you can calculate the height of the tree.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Sometimes I deliberately make mistakes, just to test you! …………….Bob Bundy

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**Monox D. I-Fly****Member**- From: Indonesia
- Registered: 2015-12-02
- Posts: 1,334

Thank you, Bob!

bob bundy wrote:

(if necessary as the tree may not be vertical)

Ah, this reminds me to when I and my friends were lost in a mountain. Almost no tree was vertical there. However, I, not even realizing that I was lost due to trusting my experienced friends, thought that such thing was normal.

Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away. May his adventurous soul rest in peace at heaven.

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