Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

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

Hi,

I got C as an answer wondering if that is correct

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

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,919

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

The knowledge of some things as a function of age is a delta function.

Offline

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

Thanks

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

Offline

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

and for this one I choose A

9. What is the value of x?

A 22.5

B 45

C 63.6

D 50

*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

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,919

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

The knowledge of some things as a function of age is a delta function.

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,912

hi zee-f

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

Bob

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

Offline

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

Isosceles Triangle?

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,912

Correct ... and therefore x = ?

Bob

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

Offline

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

45?

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,912

Yes, that's it.

Bob

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

Offline

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

Thank you

Still working on the rest 11 left

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,912

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

Bob

Offline

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

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

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,912

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

Offline

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

So I can use the Pythagoras theorem

14²+ b²= 16²

196+ b² = 256

256- 196=b²

b²= 60

b= 2√15 or 7.75

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,912

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.

Offline

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

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

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,912

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

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,912

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

Offline

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

ooooh yeah from the Transformation lesson forgot about that

KQ= 16 * 14/8

KQ= 28

NQ= 28 - 16

NQ = 12

Offline

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

Thank you

Offline

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

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

Offline

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

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°

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,912

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

Offline

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

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

Offline