<p>Help me out with this question, please. (frm Barron's Math Workbook for the new SAT, page 78)</p>
<p>4a/6a + 5/17 = 1</p>
<p>What digit does "a" represent? The book gave 8 but I don't understand the method they gave.</p>
<p>Either they made a mistake or you made one, because a=8 is not the correct answer for that question. Just take your calculator to verify. For a=8 that equation equals something about 0,96.</p>
<p>You must have made a mistake in writing out the question</p>
<p>4a/6a + 5/17 = 1</p>
<p>What digit does "a" represent? </p>
<p>the way you have it written makes "a" cancel out of the fraction</p>
<p>no, a doesnt cancel out.</p>
<p>for example, if you had 12/32, you couldnt cancel out the 2s and be left with 1/3. thats just not how it works.</p>
<p>8 is the answer. the answer key isnt wrong.</p>
<p>basically this problem is asking "what is a when 4a/6a = 12/17." do you see how i got there? i subtracted 5/17 from 1. now, there are only 10 possible answer choices (0, 1, 2, 3, 4, 5, 6, 7, 8, 9), and only five if its a multiple choice question. so i personally would solve this problem by trial and error. that is the easiest way for me to do it. if you try 8, you see that 48/68 = 12/17. 8 is the answer.</p>
<p>hopefully this makes sense. if it doesnt, i can try to explain in more detail.</p>
<p>That is pretty inconsistent and implausible.</p>
<p>4 x 8 = 32 ... not 48
6 x 8 = 48 ... not 68</p>
<p>You won't find any number that provides the necessary value to get 12/17.</p>
<p>It's asking for a digit, not a variable. So it is 48/68= 12/17</p>
<p>yeah, it is a digit. so its just 48, not 4 times 8.</p>
<p>Ahhhh, now I get it. Damn, just imagine you get such a question on your actual set and you just miss what they are asking for. I mean it´s possible.
Then you waste time and make perhaps another mistake and then you land 20 points less than you used to you. </p>
<p>Man, that's what I dislike about the test. There is that amount of luck that I cannont control. (Because it´s kinda hard as an international and non-native speaker to prepare THAT good for the SAT in about 6 months.) But that point rather accounts for the other sections; maths is ok ;).</p>
<p>yeah, i hate making stupid mistakes. on the june sat, i missed number 1 on the math section....lol. i dont remember what the question was, but i must have read it wrong or bubbled wrong or something like that. if i could just eliminate all my stupid mistakes my score would probably go up so much.</p>
<p>Jap, I know what you mean. </p>
<p>By the way, I meant 6 WEEKS and not months. If I had six months for preparation, I wouldn't feel so weird about Saturday.</p>
<p>Let's just hope that we all get very understandable exercises with reasonable questions and stop doing stupid mistakes for about 3 hours 45 minutes.</p>
<p>lol, yeah. and lets hope that i dont get a math experimental. that would drive me insane.</p>
<p>Thanks Andrea for the explanation. I never thought "a" was part of a number. I was thinking it was a variable. Drove me insane this question yesterday :)
Thanks again!</p>
<p>I know the answer has already been shown to be 8, but I want to show exactly how one could solve for a without just "noticing" that 48/68 = 1-5/17</p>
<p>4a/6a + 5/17 = 1</p>
<p>What digit does "a" represent? </p>
<p>4a/6a = 12/17
(40+a)/(60+a) = 12/17
17(40+a) = 12(60+a)
680 + 17a = 720 + 12a
5a = 40
a = 8</p>
<p>^It does work nicely.
Still, smart "noticing" might do faster.</p>
<p><4a>/<6a> + 5/17 = 1
<4a>/<6a> = 1 - 5/17
<4a>/<6a> = 12/17
<4a>/<6a> must be reduced if we want 12/17, so
<4a> is a multiple of 12.
Which forty-something is a multiple of 12?
It's 48, so <4a> = 48, and a=8.
Just to make sure,
48/68 = 12/17 indeed.</p>
<p>Of course it is faster and more efficient, but I just wanted to give a fool-proof way for somebody with perhaps less mathematical intuition to solve the problem without having to rely on an innate "noticing" ability. </p>
<p>As a matter of fact, nearly all SAT math problems can be solved extremely quickly by "noticing" little sparks in problems that lead rapidly to an answer, but they can also all be solved using routine problem-solving methods.</p>
<p>Totally agreed. Sometimes I get those sparks when I come home after the test :( (and I have taken umpteen tests). I hope I'll do better in October (SAT I), November (SAT II Math 1 and 2) and December (ACT).</p>