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**otherwiseknownaskyra****Member**- Registered: 2014-04-08
- Posts: 13

I submitted my answers to my teacher through my online course and got 18/20 correct!

But I would like to have 20/20 correct so here are the ones I missed:

7. The apothem of a regular 9-sided figure is 6 feet and the area is 117.67 square feet. What is the perimeter of the regular 9-sided figure?

A 4.36 feet

B 19.61 feet

C 39.22 feet

D 54.00 feet

I did A=bh

117.67=b(6)

19.61=b

My answer was B and it was marked incorrect.

18. In the diagram shown, a 12-foot slide is attached to a swing set. The slide makes a 65 degree angle with the swing set. Which answer most closely represents the height of the top of the slide?

A 5.0 feet

B 5.6 feet

C 10.9 feet

D 25.7 feet

I didn't know how to do this one so I guessed B which was wrong

Thank you for the help!

Making mistakes is a lot better than not doing anything. -Billie Joe Armstrong

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,363

Hi;

Doing a quick and rough check, B for the first one is incorrect. The answer is C.

For the second one answer A is correct. You would use SOHCAHTOA for this one.

Please recheck you calculations and welcome to the forum.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

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**otherwiseknownaskyra****Member**- Registered: 2014-04-08
- Posts: 13

7. I know B is incorrect, but I'm not sure how I'm supposed to end up with C.

18. In the diagram shown, a 12-foot slide is attached to a swing set. The slide makes a 65 degree angle with the swing set. Which answer most closely represents the height of the top of the slide?

cos(65)=x/12

0.423=x/12

5.076=x

That's still closer to B than A, what am I doing wrong?

Making mistakes is a lot better than not doing anything. -Billie Joe Armstrong

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**otherwiseknownaskyra****Member**- Registered: 2014-04-08
- Posts: 13

Oops, that's not closer to B than A. Apologies, I read it wrong

Making mistakes is a lot better than not doing anything. -Billie Joe Armstrong

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,363

So, you are clear on 18 now?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

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**otherwiseknownaskyra****Member**- Registered: 2014-04-08
- Posts: 13

Yeah, thanks. I still need help on 7 though, I don't really understand how I'm getting the wrong answer.

Making mistakes is a lot better than not doing anything. -Billie Joe Armstrong

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,588

hi otherwiseknownaskyra

Welcome to the forum.

The area of a 9 sided regular polygon is

Divide into 9 isosceles triangles; get area of one; then x by 9.

One triangle = half base x height = half a side x apothem = 3 x side

So whole = 9 x 3 x side

Therefore one side = 117.67 / 27

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

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,363

Hi;

Use this formula for 7.

Now solve for s. Remember to multiply by 9.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

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**otherwiseknownaskyra****Member**- Registered: 2014-04-08
- Posts: 13

Okay so,

117.67 is the area of the whole thing so 117.67/9=13.074 would be the area of one triangle

13.074/2=6.537

A=bh/2

6.537=6b/2

6.537=3b

2.179=b

And then multiply 2.179(18)=39.222 because 2.179 is just half of the length of one side

So that gives me C!

Thank you guys so much

Making mistakes is a lot better than not doing anything. -Billie Joe Armstrong

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,363

Congratulations on getting 18 out of 20 by the way.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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