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#1 2010-06-24 17:04:54

lakeheadca
Member
Registered: 2010-01-31
Posts: 37

Problem#3 Grade 11 Geometry

What Is The Length Of Ad To The Nearest Tenth Of A Centimeter?
1)3.6
2)6.0
3)6.4
4)4.0
Please Explain. Thank You.

View Image: 4.JPG

Last edited by lakeheadca (2010-06-24 17:12:40)

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#2 2010-06-24 17:17:51

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,972

Re: Problem#3 Grade 11 Geometry

Hi lakeheadca;

Did you try to form your equations like this:

a^2 + x^2 = 6^2

a^2 + (10-x)^2 = 8^2


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 2010-06-24 17:20:21

lakeheadca
Member
Registered: 2010-01-31
Posts: 37

Re: Problem#3 Grade 11 Geometry

6²+8²=c²
100=c²
10=c
10x=6²
X=3.6 Ans.
But Why 10x Multiplying With X???

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#4 2010-06-24 17:25:14

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,972

Re: Problem#3 Grade 11 Geometry

That is correct,x = 3.6. I don't understand where you do not understand.


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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#5 2010-06-24 17:28:40

ZHero
Real Member
Registered: 2008-06-08
Posts: 1,889

Re: Problem#3 Grade 11 Geometry

ADC∼CDB

AD/AC = CD/CB

x/6 = √(6² - x²)/8

Solve for 'x'


If two or more thoughts intersect with each other, then there has to be a point.

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#6 2010-06-24 17:30:34

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,972

Re: Problem#3 Grade 11 Geometry

You can subtract the top equation from the bottom one to get:

h^2 + x^2 = 6^2

h^2 + (10-x)^2 = 8^2  The h^2 will cancel when you subtract.

(10-x)^2 - x^2 = 8^2 - 6^2

100 - 20 x = 28

-20 x = -72

20 x = 72

x = 3.6


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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#7 2010-06-29 03:29:09

lakeheadca
Member
Registered: 2010-01-31
Posts: 37

Re: Problem#3 Grade 11 Geometry

ZHERO:
ADC∼CDB (One triangle looks bigger than other one????) they don't looks equal. Are you saying something about ratio

Bobby:
what is a² and what is h²
if (10-x) is AD
so DB should be 10+x or the same 10-x ???

lost again. hate Pythagorean.

Last edited by lakeheadca (2010-06-29 03:30:53)

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#8 2010-06-29 03:34:47

lakeheadca
Member
Registered: 2010-01-31
Posts: 37

Re: Problem#3 Grade 11 Geometry

I think first time you guys came across someone who is that bad in Math

Last edited by lakeheadca (2010-06-29 03:42:35)

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#9 2010-06-29 03:58:24

ZHero
Real Member
Registered: 2008-06-08
Posts: 1,889

Re: Problem#3 Grade 11 Geometry

Yea.. The triangles are "similar" and not "congruent".
Its means that all their angles are equal and their sides are "proportional".


If two or more thoughts intersect with each other, then there has to be a point.

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#10 2010-06-29 09:44:15

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,972

Re: Problem#3 Grade 11 Geometry

I think first time you guys came across someone who is that bad in Math

Calm down, I am worse. If I appear better, it is only because I have been doing it longer.

You might be getting a little confused over the fact we are using 2 different methods. Don't be. Just means you have a choice of what you like and understand best. Right now you are in school, your teachers are jamming many methods down your throat. They want you to learn all of them. When you are on your own you will get to choose what you like and are good at. I like simultaneous equations and solve many problems with them.

Bobby:
what is a² and what is h²
if (10-x) is AD
so DB should be 10+x or the same 10-x ???

No, If AB = 10 and AD = x then DB = 10 - x

a is side CD so I will out it into easier notation, sorry about the confusion.

1)   (CD)^2 + x^2 = 6^2              Triangle CDA

2)   (CD)^2 + (10-x)^2 = 8^2       Triangle BDC

Again 2 equations and 2 unknowns. If you subtract eqtn. 1 from eqtn 2 you will eliminate (CD)^2.
Can you now solve for x?


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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#11 2010-06-30 14:15:13

lindsey8555
Member
Registered: 2010-06-07
Posts: 4

Re: Problem#3 Grade 11 Geometry

Archimedes run rings around your head? Well you've come to the right place. This is where you'll find almost everything you'll ever need to know about Geometry. We have a special page on constructions and plenty of sample problems to help you understand the concepts. Have a blast and don't forget to check out our Glossary - it's huge!

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#12 2010-06-30 15:31:01

lakeheadca
Member
Registered: 2010-01-31
Posts: 37

Re: Problem#3 Grade 11 Geometry

Thank you Bobby. I got it. You made the problem easy.

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#13 2010-06-30 19:04:15

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,972

Re: Problem#3 Grade 11 Geometry

Your Welcome!


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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#14 2010-08-11 18:45:34

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,972

Re: Problem#3 Grade 11 Geometry

Hello allanmc0719


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

#15 2010-08-11 21:38:17

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,972

Re: Problem#3 Grade 11 Geometry

Hi allanmc0719;

Sorry to hear that, hope you feel better.


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

#16 2010-08-12 12:30:40

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,972

Re: Problem#3 Grade 11 Geometry

No, not me. I hate resting. But if you must then...


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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