scale factor help

zee-f · 2012-10-01 08:20:22

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

bobbym · 2012-10-01 08:22:58

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?

Bob · 2012-10-01 08:27:22

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

zee-f · 2012-10-01 08:51:40

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

bobbym · 2012-10-01 08:56:45

Hi;

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

zee-f · 2012-10-01 09:03:34

28.7 x 0.244= 7.0028 so I ignore the 0028? right

bobbym · 2012-10-01 09:07:34

Hi;

Not necessary.

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

zee-f · 2012-10-01 09:14:36

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

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

zee-f · 2012-10-01 09:20:04

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

bobbym · 2012-10-01 09:20:29

I like D.

zee-f · 2012-10-01 09:31:33

me 2 but I got D as incorrect

bobbym · 2012-10-01 09:33:59

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

Bob · 2012-10-01 18:45:37

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!

zee-f · 2012-10-03 08:41:36

It turned out to be .217 as a correct answer

bobbym · 2012-10-03 08:43:47

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

Math Is Fun Forum

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

scale factor help

#2 2012-10-01 08:22:58

Re: scale factor help

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

Re: scale factor help

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

Re: scale factor help

#5 2012-10-01 08:56:45

Re: scale factor help

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

Re: scale factor help

#7 2012-10-01 09:07:34

Re: scale factor help

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

Re: scale factor help

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

Re: scale factor help

#10 2012-10-01 09:20:29

Re: scale factor help

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

Re: scale factor help

#12 2012-10-01 09:33:59

Re: scale factor help

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

Re: scale factor help

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

Re: scale factor help

#15 2012-10-03 08:43:47

Re: scale factor help

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