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#1 2014-04-08 03:49:20

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

Geometry

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! big_smile

View Image: clip_image047.gif

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

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#2 2014-04-08 04:22:56

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,494

Re: Geometry

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.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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#3 2014-04-08 05:22:12

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

Re: Geometry

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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#4 2014-04-08 05:24:51

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

Re: Geometry

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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#5 2014-04-08 05:33:51

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,494

Re: Geometry

So, you are clear on 18 now?


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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#6 2014-04-08 05:36:05

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

Re: Geometry

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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#7 2014-04-08 05:36:06

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,528

Re: Geometry

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


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

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#8 2014-04-08 05:36:52

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,494

Re: Geometry

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.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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#9 2014-04-08 05:57:30

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

Re: Geometry

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 big_smile


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

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#10 2014-04-08 06:00:21

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,494

Re: Geometry

Congratulations on getting 18 out of 20 by the way.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

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