catchup&mustard

Hi, this math problem is from the blue book (official study guide). Prac test 2, sect 2, pg 587
I'd appreciate a solution to this problem/explanation of answer

Q19.
If a,b,c and f are four non-zero numbers, then all of the following proportions are
equivalent EXCEPT:

A) a/f= b/c

B) f/c=b/a

C) c/a=f/b

D) a/c=b/f

E) af/bc=1/1

Correct answer: A--> but why???

trakwrecka

I don't know if i have the right approach but here goes:

It says a,b,c and f are four non-zero numbers. Let's assume that a=1 b=2 c=3 f=4. Plug them in to each answer choice and you will get:

A) 1/4=2/3 NOT EQUIVALENT

B) 4/3=2/1 If you reduce 2/2 from each proportion, they are equivalent.

C) 3/1=4/2 If you reduce 1/1 from each proportion, they are equivalent.

D) 1/3=2/4 If you reduce 1/1 from each proportion, they are equivalent.

E) 1x4/2x3=1/1>>4/6 ***, not equivalent?

Uhh, I just realized I made a mistake somewhere. I'm also puzzled XD

Detreacy

if you cross multiply all you always get af=bc except for choice a

theredsmileyface

detreacy... you are amazing

Ivan_Stanchev

SUre,just cross multiply

trakwrecka

Indeed, at least i ALMOST had it. XD
And thank me too you ungrateful bastard

catchup&mustard

Thanks everyone, I appreciate all of your answers!

Bigb14

i remember messing up before on this question XD

yeah, the solution is much simpler than you think.

gcf101

Don't forget about this helpful resource:
Consolidated List of Blue Book Math Solutions, 3rd ed.