SAT Math Formulas besides the ones given on the test

Test Preparation SAT Preparation
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<p>I've been using the search function on this website, and i noticed there wasn't any particular thread dedicated to math formulas (besides the ones given in the SAT test booklet on the day of the test). Unless i just did't search well enough. I saw threads dedicated to the answers for the blue book, vocab, and etcetera. I was hoping maybe people would be kind enough to give their insight on fomulas or short cuts for the math part. To name a few of the top of my head: Price increase, price decrease, midpoint, distance, just about practically anything that has to do with the SAT. An example that i saw in a thread was a substitute for the D=RT Problems, which was (2<em>speed1</em>speed2)/(speed 1+speed2). By the way could someone explain that if it is not in the 1 HOUR UNIT. Also such things as if we could use SOH-CAH-TOA for the geometry. Maybe your thinking why don't i just go buy books and figure out the formulas like in Kaplan (math in a nutshell), but truth be told, i can't really get any SAT books like that since i have little money. So it would do me a world of pleasure and gratitude (and probably other people) if we could make a consolidated list for all the math formulas. </p>

<p>Thank you to those who submit replies</p>

2

<p>As far as formulas go, I can't think of any ones you really need... a week ago I took a practice test, and I didn't even need to look at the ones they gave-- I knew all those basic ones, and I didn't need anything I didn't know.</p>

<p>To be honest, I don't think you really need any special shortcuts or anything-- if you want to improve your score, just work on practice problems from the internet, and read their explanations. Here are some for example: <a href="http://www.majortests.com/sat/index.php%5B/url%5D"&gt;http://www.majortests.com/sat/index.php&lt;/a&gt;&lt;/p>

<p>Another helpful thing is College Board's SAT question of the day... sign up for that. They have math questions, sentence completions, and sentence error ones.</p>

<p>Also, have you checked your library for SAT books? They should have some you could borrow...</p>

3

<p>Thanks for the reply, but do you know anything about the one formula about distance (2<em>speed1</em>speed2)/(speed 1+speed2) i mentioned up there. I can't think of an application to apply that formula to, does anybody know a good problem besides the one mentioned in Xiggi's test prep advice. One that is not in the hour's unit.</p>

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<p>It's not really necessary, but knowing about permutations/combinations can help you solve those types of problems quicker. A lot quicker than writing down combinations by hand and then adding them up, at least. I can't really remember the formulas right now, but just a basic understanding of factorials and how to input them on the calculator saves a lot of time, EX: "'6<em>5</em>4<em>3</em>2*1' vs. '6 [MATH] [<-] 4'"</p>

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<p>My calculator just has a factorial button. You just put in 6!</p>

<p>And I've never heard of that speed formula thing.</p>

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<p>permutations/combinations</p>

<p>What are those exactly? Any sample questions (they can be simple).</p>

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<p>Permutations is a set of things arranged in a different order, like ABC, ACB, BAC, BCA, CAB, CBA.</p>

<p>With combinations, the order of things doesn't matter-- it matters which ones get picked. Like if someone has five shirts, two pairs of pants, and three hats, how many possible combinations of outfits does the person have? (You multiply 5 x 2 x 3)</p>

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<p>In that situation, why/how would you use factorials?</p>

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<p>If I remember correctly, you use factorials for permutations, not combinations. For the ABC example I gave, the answer would be 3! (3 factorial). Because if you have 3 letters, for the first one, there are three choices, then for the second one, you've already used up one letter, so there are 2 choices left, and then for the third one there's only one choice. So it's 3x2x1, which is 3!.</p>

<p>Did that make sense?</p>

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<p>I never looked at the formulas when I took the SAT. I doubt any top scorers do.</p>

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<p>"I never looked at the formulas when I took the SAT. I doubt any top scorers do."</p>

<p>Yeah... they're so basic that anyone who's had a few years of high school or even middle school math would (should!) know them already...</p>

12

<p>Yeah... I got stuck on a triangle problem and the end of a section. Then I discovered the front page had the angles and formulas I needed.</p>

<p>I believe it's helpful to know they are there and use them if necessary. Also, some top scorers do (at least one).</p>

<p>If you aren't comfortable with math, or you want to go faster, I recommend borrowing a TI89 from someone. It has the solve function and host of other useful features.</p>

13

<p>
[quote]
If I remember correctly, you use factorials for permutations, not combinations. For the ABC example I gave, the answer would be 3! (3 factorial).

[/quote]
</p>

<p>This is coincidence. A permutation is (n!)/(n-k)!. In this situation it is how many ways are there to arrange three letters in three spots. Thus, n=3, as does k. You get 3!/(3-3)! = 3!/0! = 3! = 6.</p>

<p>For combinations it is just (n!)/[k!(n-k)!] if I remember right.</p>

<p>This is based of memory, so I'm not 100% sure, but I think that's how it works.</p>

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<p>I don't get the types of problems with permutation.</p>

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<p>Oh yeah, I do remember something like that from way back in prealgebra...</p>