December 2010 SAT Math

Test Preparation SAT Preparation
881

<p>I’m not sure I follow (but then again, math is my weakest subject haha). </p>

<p>I rationalized it using the actual problem, as such:</p>

<p>given a starting point (1980, 13), the graph could progress with 11 additional points.</p>

<p>(1982, 14)
(1984, 15)
(1986, 14)
(1988, 15)
(1990, 16)
(1992, 15)
(1994, 16)
(1996, 17)
(1998, 16)
(2000, 17)
(2002, 18)</p>

<p>The change in the graph is calculated as (each in absolute value) (15-14)+(14-15)+(15-14)+(16-15)+(15-16)+(16-15)+(17-16)+(16-17)+(17-16)+(18-17) = 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 = an overall change of 10, which is y2-y1</p>

<p>The undisputed X change, of course, is 2002-1980, or 22. </p>

<p>10/22 = 5/11 = .4545454545 (or something like that?), which is close to 1/2.</p>

<p>Again, I could be wrong – but this is how I saw it.</p>

<p>edit: you added -4 to a positive number; however, because we’re dealing in change, should it not be an absolute value? Instead of -4, should not 4 be added? that would give 14/2, or 7 (conveniently twice of 3/2, as 1/2 is of 1/4)</p>

882

<p>^ Uh, you dont take into account the little changes in between the initial and the final point. </p>

<p>Inital: (1980, 13)
Final: (2002, 18)</p>

<p>Do rise/run = 1/4.</p>

883

<p>Why don’t you? The question does not ask for average increase. If it did, then we would add negatives as negatives. It asks for average change, so any change – positive or negative – counts.</p>

884

<p>-4 indicates it went downward in that interval.
A way to calculate the AVERAGE slope is by adding up all the slopes and dividing by how many # of slopes you calculated. The method I just showed is the long and unneeded method that just proves “delta y over delta x” is equal to average slope.</p>

<p>EDIT:

</p>

<p>This could be true. Although I’m doubtful. Does anyone remember the EXACT wording of the problem?
I think it was “the average change in consumption of potatoes per year”?</p>

<p>I think there were two “per” in what it was asking for.</p>

885

<p>"Wait how is it 2.40 for the auto-industry problem? </p>

<p>I made one stupid mistake already. Do NOT want another."</p>

<p>Anyone want to respond to this?</p>

886

<p>I understand that -4 indicates that it went downward. </p>

<p>But why are we distinguishing between downward and upward? Everything is a change. If the graph oscillated to a million and to 0 a hundred times before eventually ending up at 18, would we call the average change 1/4? That’s what I have trouble grasping.</p>

887

<p>I hope what somestudent is saying is right =)</p>

888

<p>@somestudent2, I understand where you are coming from. I understand why you used the absolute value. The thing that I don’t remember is the exact wording of the question. The exact wording will indicate whether 1/4 or 1/2 is correct. </p>

<p>Does anyone remember the exact wording of the question?</p>

889

<p>I’m glad we agree on the math end of it! Now, we just have to wait until the collegeboard deigns to tell us (or not tell us, depending on whether we decide to get QAS haha). </p>

<p>I just figured that there had to be some kind of sneaky trick in there, because it was the last question of the section.</p>

890

<p>This 60 pages long thread just took a unexpected turn thanks for somestudent [:)]</p>

891

<p>Ya, it would make sense that it COULD be 1/2, after all it is a #20 question. Also I think if #20 is equal to 1/2 the curve might just be -1 = 800. :)</p>

892

<p>Well if this helps. I puty=.25x+13 into my calculator and it went through some points on the graph:)</p>

893

<p>@protosig,</p>

<p>Yes, that’s most likely close to the function of the graph. The thing is the summation of the slopes / 22 = around 1/2. The average change in the slopes delta y over delta x = around 1/4.</p>

<p>We need to know the exact question to know if the answer was either 1/4 or 1/2 since 1/4 and 1/2 answer two different things.</p>

894

<p>I just talked to my econ teacher dad. He says that the rate of change refers to a percentage which has to be the 1/4 divided by the original amount (13) times 100 percent. Which comes out to 2. -__-</p>

895

<p>Also, I clearly remember it asked for “the average rate of change” not just the rate of change. I dont know if it helps. I read the average part like 10 times trying to understand why its there</p>

896

<p>does anyone remember what section the question was that had to do with 6 boxes and 12 boxes and the answer was 72? do u remember what secttion it was in? or what number it was? or what answer choice 72 was???</p>

897

<p>^Well, my dad says “average rate of change”=“average growth rate” which is 2. I think our best bet is to hope that everybody got it wrong or to petition CB saying that their question was vague since “in pounds per person per year” implies that that’s the unit (as opposed to percent). In addition, there were no percentage signs after the answer choices.</p>

<p>EDIT: <a href=“http://www.ehow.com/how_4532706_calculate-growth-rate-percent-change.html[/url]”>http://www.ehow.com/how_4532706_calculate-growth-rate-percent-change.html&lt;/a&gt;&lt;/p&gt;

898

<p>If the wording was, “average rate of change”, mathematically it refers to change in value or change in time. The in pounds per person per year indicates it is asking for the yearly change in consumption of potatoes in pounds per person.</p>

<p>In this case it was 5 pounds of potatoes / 22 years = .227 pounds of potatoes consumed by each person per year.</p>

<p>It must be 1/4.</p>

899

<p>^I REALLY REALLY REALLY hope you’re right. A lot depends on the vague wording of the question. But if you read the eHow link I posted, it’s asking for growth rate.</p>

<p>That being said, could this work? <a href=“http://talk.collegeconfidential.com/sat-preparation/1044516-petitioning-sat-question.html[/url]”>http://talk.collegeconfidential.com/sat-preparation/1044516-petitioning-sat-question.html&lt;/a&gt;&lt;/p&gt;

900

<p>We could riot:)</p>