Can you solve this uber-hard math problem?

Test Preparation SAT Preparation
1

<p>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</p>

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

<p>A) a/f= b/c</p>

<p>B) f/c=b/a</p>

<p>C) c/a=f/b</p>

<p>D) a/c=b/f</p>

<p>E) af/bc=1/1</p>

<pre><code> Correct answer: A--> but why???
</code></pre>

2

<p>I don't know if i have the right approach but here goes:</p>

<p>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:</p>

<p>A) 1/4=2/3 NOT EQUIVALENT </p>

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

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

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

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

<p>Uhh, I just realized I made a mistake somewhere. I'm also puzzled XD</p>

3

<p>if you cross multiply all you always get af=bc except for choice a</p>

4

<p>detreacy... you are amazing</p>

5

<p>SUre,just cross multiply</p>

6

<p>Indeed, at least i ALMOST had it. XD
And thank me too you ungrateful bastard :)</p>

7

<p>Thanks everyone, I appreciate all of your answers!</p>

8

<p>i remember messing up before on this question XD</p>

<p>yeah, the solution is much simpler than you think.</p>

9

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