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#1 2012-10-01 08:20:22

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

scale factor help

Find the scale factor of each if the polygons are proportional

A = 7, 7, 21, 23 B = 28.7, 28.7, 86.1, 94.3

I choose A and I am still kind of confused because I divided 7/28.7 and got 0.2439024 in the calculator but when I did it I got 4.1

A  Prop, s.f. = 0.244
B  Prop, s.f. = 0.215
C  Prop, s.f. = 0.284
D  Prop, s.f. = 0.297
E   Prop, s.f. = 0.236
F   Prop, s.f. = 0.212


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 2012-10-01 08:22:58

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,429

Re: scale factor help

Hi;

I divided 7/28.7 and got 0.2439024 in the calculator but when I did it I got 4.1

You went backwards on that calculation with the calculator?


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

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#3 2012-10-01 08:27:22

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,092

Re: scale factor help

It just depends on whether you do (A divided by B) or (B divided by A).

If the second shape has got smaller you want a fraction for the scale factor and if it has got bigger you want a number over 1.

Yet it seems your course teachers have this back to front ???

No problem as long as the questions are consistent about this.

Bob


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

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#4 2012-10-01 08:51:40

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

Re: scale factor help

A = 7, 7, 21, 23 B = 28.7, 28.7, 86.1, 94.3

I got A as correct but like I rounded 0.2439 to 2440 is that a correct option? or is there another way to get the answer.

A  Prop, s.f. = 0.244
B  Prop, s.f. = 0.215
C  Prop, s.f. = 0.284
D  Prop, s.f. = 0.297
E   Prop, s.f. = 0.236
F   Prop, s.f. = 0.212


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 2012-10-01 08:56:45

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,429

Re: scale factor help

Hi;

That is what I got too. Did you check it?


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

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#6 2012-10-01 09:03:34

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

Re: scale factor help

28.7 x 0.244= 7.0028 so I ignore the 0028? 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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#7 2012-10-01 09:07:34

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,429

Re: scale factor help

Hi;

Not necessary.

.2439 can be rounded to .244. That is why I like A.


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

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#8 2012-10-01 09:14:36

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

Re: scale factor help

I answered 5-D 8-D 9-E 10-B and they were all incorrect So I revised it and here is what I got wondering if it is correct

5. A because 9/41.4 gives me 0.2173913

but when I check it its wrong neutral

5. A = 9, 10, 16, 19  B = 41.4, 46, 73.6, 87.4
A Prop, s.f. = 0.217
B Prop, s.f. = 0.318
C Prop, s.f. = 0.421
D Not prop
E Prop, s.f. = 0.294
F Prop, s.f. = 0.721


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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#9 2012-10-01 09:20:04

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

Re: scale factor help

41.4 divided by 9 gives be 4.6 and when I check it it is correct why do they give us such weird decimal confusing numbers it confuses me and it gets annoying


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 2012-10-01 09:20:29

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,429

Re: scale factor help

I like D.


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

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#11 2012-10-01 09:31:33

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

Re: scale factor help

me 2 but I got D as incorrect


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 2012-10-01 09:33:59

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,429

Re: scale factor help

What did they say the answer was? It really should be A.


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

#13 2012-10-01 18:45:37

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,092

Re: scale factor help

hi zee-f

Answer A is the correct answer.

If your teacher has a different answer on the markers sheet ask that it be corrected.

You may use the evidence below.

Bob

ps.

41.4 divided by 9 gives be 4.6 and when I check it it is correct why do they give us such weird decimal confusing numbers it confuses me and it gets annoying

Yes, you are right.  If shape A is transformed into B using a scale factor the correct way to compute the sf is to calculate B/A.

I don't know why they have this back to front, but you can get their answers by doing A/B so it looks like you'll have to live with this.  Just be prepared to do it properly when you meet scale factors elsewhere!

View Image: zeefprop.gif

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

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#14 2012-10-03 08:41:36

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

Re: scale factor help

It turned out to be  .217 as a correct answer 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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#15 2012-10-03 08:43:47

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,429

Re: scale factor help

Kaboobly doo! Oh wait, I liked A too. Brilliant answer then.


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

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