<p>If f(x,y) =(x+y,y) for every pair (x,y) in the plane, for what points (x,y) is it true that (x,y) =(y,x)?
A (0,0) only
B (1,1) ONLY
C the set of points (x,y) such that y=0
d The set of points (x,y) such that x=y
E The set of points (x,y) such that 2x=y</p>
<p>I need help big time. I always mess up this time of questions. Is there no solution apart from plugging. There just has to be some way.</p>
<p>This stupid logic question also stomped me.
Suppose the following statements are true:
I All sunny days are warm
ii Some, but not all, sunny days are warm</p>
<p>Which of the folloeing statements must be false?
A All warm days are sunny
B All warm days are dry
C Some warm days are sunny
D Some warm days are dry
E All dry days are warm</p>
<p>Help anyone. Just break this down and give me tips on how to solve similar question s in future.</p>
<p>Jim owns a small business. By Jim's estimate, he has a 40% chance of making a $5000 profit in the next year and a 60% chance of losing $2000. If an expected profit is the product of a profit and the probability of making that profit , what is Jim's expected profit in the next year?
A -$200
B 4800
C $2200
D $3000
E $7000
I thought the answer was going to be 0.4*5000 but the answer was 0.4(5000)+0.6(-2000). Whhhhyyy is this so? I am still ransacking my brain as to wwwhhhyyyyyyy</p>
<p>haha I did this set of questions yesterday...
ok for the first one
all you have to do is plug in the points and see which one fits the description and (0,0) is the only one that works because (0+0, 0) is the same as (x,y) switched to (y,x)
^^ sounds confusing but that's all there is to it =/</p>
<p>I also missed the logic question</p>
<p>as for the expected gain, this is something that a statistics course will teach you:
expected gain=(probability of profit X the profit)+(probability of loss X the loss)...the description they gave you in the question was completely bogus and that threw me off at first but yea</p>
<p>hope this helps</p>
<p>Hahah I did this one too!</p>
<p>I think that #3 was choice B, which was $800.</p>
<p>Is Sparknotes harder than the real math ii. I have never finished and I keep getting 730. My aim is 800, but the test date isjust 2 days from now. Damn. I am pretty fustrated. Am I within range.</p>
<p>Start omitting questions which bog you down. It' imperative to keep a good pace.</p>
<p>Sparknotes are quite close to the real thing - just a little easier and don't include standard deviation (I think).</p>
<p>There IS a solution to the first question apart from plugging. Here it is.
set (x+y,y) = (y,x)
The x coordinates have to be equal and the y coordinates have to be equal:
x+y=y
thus, x=0
y=x
thus, y =0
Answer should be A, (0,0) only. Yes?</p>
<p>For the second question, are you sure you copied that down correctly? The two "true" statements are contradictory...</p>
<p>Agreed, Q2 seems to contradict itself</p>
<p>yea that second part should read: some, but not all, sunny days are dry</p>
<p>The heights of all American children of a particular age are
normally distributed with a mean of 48 and a standard deviation of
1.8. If an American student of this age is 52 inches tall, which of
the following best describes the percentile that student is in?
(A) 50th
(B) 52nd
(C) 84th
(D) 95th
(E) 99th</p>
<p>The answer is E. Why?</p>
<p>@YoungSookim</p>
<p>imagine a bell curve with the center at 48. by assuming that this is normally distributed, we can use the 68-95-99.7 rule. Each std dev. is 1.8 so 52 is about 4 std dev. out from the mean. 1 std dev contains 68%, 2 std dev contains 95, 3 std dev contains 99.7, 4 std dev contains even more. </p>
<p>I think that’s how you do it. I took AP Stats this year, but I’m not sure if that’s how you would do it.</p>
<p>also, is binomial theorem going to be on the test?</p>
<p>Thank you vbpointer42 but I don’t understand how 52 is 4 std dev out from the mean, is it just 52 - 48? or is the 1.8 relevant, I don’t see how it is not relevant. I was thinking 4 / 1.8 so it is more than 2 std dev off the mean but less than 3. Still a little confused…</p>
<p>As far as I could tell, it doesn’t come up often. I think it is a Barron’s thing and nothing more. If you have a TI-89, the calculator will expand the Binomial for you so it is simple. F2, then Expand.</p>
<p>Q2 should be B. A could be false (there could be cloudy days where it’s warm), but it asks for which must be true. </p>
<p>If you think of the two statements as:
-Monday through Saturday, it is sunny and thus warm
-Monday and Tuesday, it is sunny and dry
-Sunday it is cloudy and the temperature and dryness are unknown</p>
<p>then it is impossible for all warm days to be dry.</p>
<p>@youngsookim I think that answer should be 95th percentile. 52 is ~2 deviations from the mean, which corresponds to the 95th percentile (1 sd = 68%, 3 sd = 99.7%)</p>
<p>I would use elimination for the standard deviations question. Since the standard deviation is 1.8, that means 52 is (52-48)/1.8 =~= 2.2 standard deviations from the mean. Since 95th percentile occurs @ 2 standard deviations, but this is over 2, the answer must be 99th. </p>
<p>I think my reasoning is off a little, haven’t taken stat but self studied it. Anybody want to confirm what I said above?</p>
<p>You are right! EducationOD, that makes sense, the 95th does occur at 2 std, so it must be 99. 
Thanks everyone, that was terrific! I will also try to participate if I can.</p>