3 Math Problems (Help)

<p>Wait am I not allowed to put test questions on here? It's from the January test. If I am allowed, someone please post and I wll repost my questions...</p>

<p>its perfectly fine. wat is it</p>

<p>Hi I am having trouble with these 2 questions. They are from the January test a few months back…</p>

<ol>
<li>The cost of a piece of a cetain type of lumber is directly proportional to its length. A piece of this lumber that is 8 feet long costs $6.00. What is the cost, in dollars, of a piece of this lumber that is y yards long? (1 yard = 3 feet)</li>
</ol>

<p>A) y - 2</p>

<p>B) 3y - 2</p>

<p>C) (3/4)y</p>

<p>D) (9/4)y</p>

<p>E) 4y</p>

<p>Okay…*** is this…Its wording is confusing and I’m clueless…</p>

<ol>
<li>At North High School, the ski club has 15 members and the debate club has 12 members. If a total of 11 students belong to only one of the two clubs, how many students belong to both clubs?</li>
</ol>

<p>A) 2</p>

<p>B) 7</p>

<p>C) 8</p>

<p>D) 12</p>

<p>E) 16</p>

<p>These problems always rape me and once I learn it I always forget the method. </p>

<p>THank you if you can help</p>

<p>^ How did you do the integer question?</p>

<p>I want to know.</p>

<p>Oh for the integer question, you choose the smallest number possible for x and the bigget number possible for y so x/y would be as small as possible. These two I am still having trouble with! =P</p>

<ol>
<li>Set up a proportion (x=ky). You could make x the price and y the length, for convenience. So we have, as given, that</li>
</ol>

<p>6=8k</p>

<p>Thus k=3/4</p>

<p>Now, we set in the variable y (for yards, this time) into the original equation, since we now know what k equals:</p>

<p>x=(3/4)y</p>

<ol>
<li>I didn’t feel like going through the logical underpinnings of this problem, so I just did a simple system of equations, but you could always just draw Venn diagrams and see what works. What I did follows:</li>
</ol>

<p>Let x equal the number of students in one club, and y equal those in both clubs. Now, the information for the question gives you:</p>

<p>x=11</p>

<p>But we can set up another equation. We will tally up the population of each club individually. However, some students will be counted twice (y: those in both clubs). So the total club count equals 15+12=27, so the other equation could be</p>

<p>x(those in one club)+2y(those in both clubs)=27(the tally of both clubs combined)</p>

<p>Substitute 11 in for x and solve y for 8.</p>

<p>I hope that was clear… it seemed to get more and more convoluted as I went through it, though. Good luck tomorrow.</p>

<p>^wrong. dont even know what you think the answer for the second question is, but ill just explain it…</p>

<p>17 is D. it states DIRECTLY proportional (think DIrectly proportional = DIvide). this is how you set-up the problem. </p>

<p>the problem asks in yards, so you want the 8 feet into yards. </p>

<p>(8/3)/6 = y/x (x = cost of lumber of y-yards long)
4/9 = y/x
4x = 9y
x = (9/4)y </p>

<p>19 is E. 15 belong to ski, 12 to debate club, meaning that including the members who are in both, there are 27. they tell you that 11 are in EITHER OR. (for example 5 in ski and 6 in debate; these 11 are NOT members of both). if drawing a venn-diagram will help, do it. It’s asking how many people are in the intersection of the venn-diagram, so the total amount of members is 27. you have 11 that are exclusively in one of the two clubs. 27 - 11 = 16. you can check this answer because using my example, 5 in ski and 6 in debate, 16 members in the middle (meaning theyre in both clubs), add 10 to the ski club, and add 6 to debate. Now, you’ve fulfilled the information given of 15 members in ski and 12 in debate.</p>

<p>16 is wrong because you need to divide it by 2 since there are 2 clubs, the answer is 8</p>

<p>^ But doesn’t it ask you how many students belong to both clubs? It didn’t ask for the amount of students in one club.</p>

<p>"16 is wrong because you need to divide it by 2 since there are 2 clubs, the answer is 8 " </p>

<p>that made no sense whatsoever. it asks for the amount of people that are members in BOTH clubs. Draw a venn-diagram and you will see that 8 does not make sense. why you tryna fix somethin that aint broken…</p>

<p>if you set up and equation the answer will be 8.</p>

<p>let x = total students in both the ski and the debate club</p>

<p>so we can have two expressions:</p>

<p>15-x (number of students only in the ski club)
and
12-x (number of students only in the debate club) </p>

<p>which add together to equal to 11 because it says that 11 is the number of students in only one of the clubs, not both</p>

<p>then 15-x + 12 - x = 11
-2x +27 = 11
-2x = -16
x=8</p>

<p>

</p>

<p>The flaw in this is that this is what they WANT you to think. 15 belong to ski and 12 belong to debate. There are not 27 kids. Realize that some of the 15 in the ski club are part of the 12 in the ski club. Watch out for those kinds of things… it takes a lot of SAT practice to recognize that kind of deception.</p>

<p>17 is D
19 is C</p>

<ol>
<li>15 + 12 = 27
27 - 11 = 16</li>
</ol>

<p>Question is how many to both clubs?
both = 2
16 = 2x
x = 16/2
x = 8</p>

<p>Sorry about getting the first one wrong. Overlooked that it was in yards, but my method was alright.</p>

<p>And I did get the second one right, I just may not have explained it correctly.</p>