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#1 2012-12-15 04:16:10

zee-f
Member
Registered: 2011-05-12
Posts: 1,220

Geometry review

Hi,

I got C as an answer wondering if that is correct smile

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
B19.61 feet
C39.22 feet
D54.00 feet


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#2 2012-12-15 05:12:37

anonimnystefy
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From: The Foundation
Registered: 2011-05-23
Posts: 14,813

Re: Geometry review

C is correct. Good work!


“Here lies the reader who will never open this book. He is forever dead.

“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

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#3 2012-12-15 05:56:52

zee-f
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Registered: 2011-05-12
Posts: 1,220

Re: Geometry review

Thanks big_smile


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#4 2012-12-15 05:57:53

zee-f
Member
Registered: 2011-05-12
Posts: 1,220

Re: Geometry review

and for this one I choose A

9. What is the value of x?

A 22.5
B 45
C 63.6
D 50

View Image: clip_image026.gif

Last edited by zee-f (2012-12-15 05:58:30)


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#5 2012-12-15 06:12:13

anonimnystefy
Real Member
From: The Foundation
Registered: 2011-05-23
Posts: 14,813

Re: Geometry review

Hi

That is not correct.


“Here lies the reader who will never open this book. He is forever dead.

“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

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#6 2012-12-15 06:40:27

bob bundy
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Registered: 2010-06-20
Posts: 6,094

Re: Geometry review

hi zee-f

What sort of triangle is ABD (yes right angled but what else ?)

Bob

View Image: zeef apothem.gif

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

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#7 2012-12-15 08:30:37

zee-f
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Registered: 2011-05-12
Posts: 1,220

Re: Geometry review

Isosceles Triangle?


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#8 2012-12-15 09:14:38

bob bundy
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Registered: 2010-06-20
Posts: 6,094

Re: Geometry review

Correct ... and therefore x = ?

Bob


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

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#9 2012-12-15 10:34:55

zee-f
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Registered: 2011-05-12
Posts: 1,220

Re: Geometry review

45?


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#10 2012-12-15 10:53:35

bob bundy
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Registered: 2010-06-20
Posts: 6,094

Re: Geometry review

Yes, that's it.

Bob


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

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#11 2012-12-15 11:19:31

zee-f
Member
Registered: 2011-05-12
Posts: 1,220

Re: Geometry review

Thank you smile

Still working on the rest 11 left


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#12 2012-12-15 11:20:27

bob bundy
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Registered: 2010-06-20
Posts: 6,094

Re: Geometry review

OK.  You know where to come if you are stuck.  smile

Bob


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

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#13 2012-12-15 11:24:31

zee-f
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Registered: 2011-05-12
Posts: 1,220

Re: Geometry review

Ok So can I cut the trapezoid into a square and a right triangle?
So the triangle side would be 8

10. In the diagram shown,line  PN     is parallel to line JQ   , KN =16  centimeters,  PN= 8 centimeters, and JQ = 14 centimeters. Determine the length of  line NQ.

A 28 cm
B 12 cm
C 9.1 cm
D 7 cm

View Image: clip_image033.gif

One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#14 2012-12-15 11:28:21

bob bundy
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Registered: 2010-06-20
Posts: 6,094

Re: Geometry review

Triangle KJQ will have the same angles as KPN.

So it is an exact enlargement (do you say dilation?)

So you can use 8 ----> 14 to work out the scale factor

and apply to  16 ----> KQ

Bob


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

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#15 2012-12-15 11:41:08

zee-f
Member
Registered: 2011-05-12
Posts: 1,220

Re: Geometry review

So I can use the Pythagoras theorem

14²+ b²= 16²
196+ b² = 256

256- 196=b²
b²= 60
b= 2√15 or 7.75


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#16 2012-12-15 11:52:49

bob bundy
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Registered: 2010-06-20
Posts: 6,094

Re: Geometry review

You don't need Pythag.  It is simpler than that.

In my diagram, I've split away the larger triangle so you can see the enlargement effect more clearly (I hope).

So 8 gets enlarged to become 14.  That's a scale factor of x 14/8

Apply the same scale factor to 16 and you will get KQ.

Youi'll still have to do a subtraction to get NQ

Bob

ps.  You are not told there is a right angle so that's another reason for avoiding Pythag.  I know it looks like 90 but it might not be.

View Image: zeef enlargement.gif

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

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#17 2012-12-16 00:21:21

zee-f
Member
Registered: 2011-05-12
Posts: 1,220

Re: Geometry review

a bet confused because I don't remember taking dilation but
triangle KPN I get the following information :

opposite = 13.8564
hypotenuse = 16
adjacent = 8

and I get a 90 60 30 angle


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#18 2012-12-16 00:26:07

bob bundy
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Registered: 2010-06-20
Posts: 6,094

Re: Geometry review

hi zee-f

http://www.mathisfunforum.com/viewtopic.php?id=18566

post 6

Give me a moment and I'll come up with a better explanation for the latest problem.

Bob


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

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#19 2012-12-16 00:52:10

bob bundy
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Registered: 2010-06-20
Posts: 6,094

Re: Geometry review

Right.  One step at a time.

(i)  Why you cannot use Pythagoras' theorem:-  That angle that looks like 90 degrees may not be.  The question doesn't say it is.  Maybe it is 89 ?

And even if it is, working out KP doesn't get you any nearer to working out NQ.

(ii) This is a problem about enlargement, not Pythagoras.  On the MIF teaching pages it is called 'Resizing'.

Have a look at

http://www.mathsisfun.com/geometry/resizing.html

I think you must have done it because it was on the transformations thread.

Have a look at both links and make sure you are clear about that.

(iii)  I've taken your diagram and tried to show how the points J and Q are made by stretching the shape away from the centre at K.

P is stretched to J and N is stretched to Q.

A transformation like that is what I call an enlargement.  But on your transformation thread the question said dilation, and bobbym used the same word, so maybe that's just the difference between UK english and USA english.

Whatever,  my point is:- the triangle KPN has got bigger and the new bigger triangle is KJQ.

If it had got twice as big the scale factor would be x2.  Three times as big would be x3.

In this problem it isn't as much as x2 because JQ is only 14 not 16.

So how can you work out the scale factor this time.

So

and then

Bob

View Image: zeef enlargement2.gif

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

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#20 2012-12-16 03:41:21

zee-f
Member
Registered: 2011-05-12
Posts: 1,220

Re: Geometry review

ooooh yeah from the Transformation lesson forgot about that

KQ= 16 * 14/8
KQ= 28

NQ= 28 - 16

NQ = 12


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#21 2012-12-16 04:33:40

zee-f
Member
Registered: 2011-05-12
Posts: 1,220

Re: Geometry review

Thank you big_smile


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#22 2012-12-16 05:21:52

zee-f
Member
Registered: 2011-05-12
Posts: 1,220

Re: Geometry review

I submitted my work I got 12/20 So 8 wrong sad


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#23 2012-12-16 05:45:17

zee-f
Member
Registered: 2011-05-12
Posts: 1,220

Re: Geometry review

I choose B because Complementary angles are two angles whose measures total 90 degrees.

90 - 35 = 55 and it was incorrect.

1. Two angles are complementary. The smaller angle is 35°   less than the larger angle. What is the measure of the larger angle?

A- 27.5°   
B- 55°
C- 62.2°
D- 125°


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#24 2012-12-16 06:47:50

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,094

Re: Geometry review

hi zee-f

NQ = 12 is what I what I got too.

Complementary angles add up to 90

The question doesn't say "Two angles are complementary. The smaller angle is 35°. What is the measure of the larger angle?

It says "Two angles are complementary. The smaller angle is 35°   less than the larger angle. What is the measure of the larger angle? 

Do you see the difference?

So if the larger one is x the smaller one is (x-35) and together they add up to 90.

Bob


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

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#25 2012-12-16 08:43:04

zee-f
Member
Registered: 2011-05-12
Posts: 1,220

Re: Geometry review

So the equation would be x + y - 35 = 90 right?


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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