Al About Xiggi's Formula

Test Preparation SAT Preparation
1

<p>All*</p>

<p>Okay so with Xiggis method (not really his - its just a physics formula that he found out that he could use on the distance problems) i know there has been some speculation going on and so i had my very own questions and for anyone else who has questions on it can post it here.</p>

<p>The formula : 2 * rate1 * rate2 / rate 1 + rate 2</p>

<p>1) What exactly does this formula give you?</p>

<p>2) When do you know , after doing this formula, that the answer that you got is the answer? I know sometimes you have to divide by two or something? When is that and why?</p>

<p>Any examples pertaining to any question is greatly appreciated.</p>

<p>Thanks </p>

<p>All questions about xiggi can go in this thread!</p>

2

<p>I believe it's to find a harmonic mean. 2xy/x+y
I'm not sure of the cases that you have to divide by two. Maybe it has something do with distances.</p>

3

<p>It gives you the average speed, which, since it's in miles per hour, and since the time is one hour, is also the distance. However, Xiggy's point was that this formula, while necessary for a question that appears in the grid-in section, is not necessary.</p>

<p>Sample problem:</p>

<p>Bob drives from home to work and back. The trip takes him one hour. He averages 40mph there and 50mph. How far did he drive?</p>

<p>"How far did he drive" = distance traveled in one hour = average mph</p>

<p>a) 40
b) something around 44
c) 45
d) something around 46
e) 50</p>

<p>In this type of problem, the answer is ALWAYS slightly less than the average of the two speeds (40 and 50), ergo, the answer is b. Time to solve = 4 seconds. Just make sure you reread the question. I got one of these wrong on a practice test because the question was only asking for the distance one way. But then Adam Robinson yelled at me and made me reread the questions after I answer them.</p>

4

<p>What if this is a grid-in question (like in the Blue Book)?</p>

5

<p>For whatever reason this question is the most frequently asked one on the CC on my memory. Goes back farther back then
<a href="http://talk.collegeconfidential.com/sat-act-tests-test-preparation/36812-sat-math-question-help.html?highlight=distance%5B/url%5D"&gt;http://talk.collegeconfidential.com/sat-act-tests-test-preparation/36812-sat-math-question-help.html?highlight=distance&lt;/a&gt;&lt;/p>

6

<p>^"Goes back farther back then" -huh? what did I mean?:confused:
I guess, Goes back farther then 02-26-2005, 03:14 PM thread.</p>

<p>To make sure the relevant link is not overlooked:
<a href="http://talk.collegeconfidential.com/sat-act-tests-test-preparation/75306-math-help.html%5B/url%5D"&gt;http://talk.collegeconfidential.com/sat-act-tests-test-preparation/75306-math-help.html&lt;/a&gt;&lt;/p>

7

<p>Can't help quoting myself.:o
<a href="http://talk.collegeconfidential.com/sat-preparation/452281-question-distance-problems.html#post1059682256%5B/url%5D"&gt;http://talk.collegeconfidential.com/sat-preparation/452281-question-distance-problems.html#post1059682256&lt;/a&gt;&lt;/p>

8

<p>Is this the first appearance?
<a href="http://talk.collegeconfidential.com/sat-act-tests-test-preparation/28224-qs-full-length-sat-collegeboard-com.html?#post329850%5B/url%5D"&gt;http://talk.collegeconfidential.com/sat-act-tests-test-preparation/28224-qs-full-length-sat-collegeboard-com.html?#post329850&lt;/a&gt;&lt;/p>

9

<p>I am done with digging!
Just two more [later] appearances:</p>

<p><a href="http://talk.collegeconfidential.com/sat-preparation/68210-xiggi-s-sat-prep-advice.html?#post896778%5B/url%5D"&gt;http://talk.collegeconfidential.com/sat-preparation/68210-xiggi-s-sat-prep-advice.html?#post896778&lt;/a&gt;&lt;/p>

<p><a href="http://talk.collegeconfidential.com/sat-preparation/68210-xiggi-s-sat-prep-advice-5.html?#post1040117%5B/url%5D"&gt;http://talk.collegeconfidential.com/sat-preparation/68210-xiggi-s-sat-prep-advice-5.html?#post1040117&lt;/a&gt;&lt;/p>

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<p>That formula is to find the harmonic mean.
This formula is very useful in the average speed questions that are so frequently asked in the SAT.
Divide by two? I think its multiply by two to find the total distance covered.</p>

11

<p>Yes! Found it…</p>