10Real SATS red book 3rd edition Math problems HELP!

Test Preparation SAT Preparation
1

<p>Math problems that I could'nt get ALL FROM THE REALSATS 3rd edtion red book, please explain to me the way u would to a monkey because I truly don't understand any of these:</p>

<p>p389 #2 </p>

<p>page390 #3. what is the least number of 2's that can be multiplied together to yield a number greater than 50?
a)4
b)5
c)6
D)7
e)10</p>

<p>p390, #5. If e, f, g, and h are consecutive odd integers and e<f<g<h , then g+h is how much greater than e+f?
a)2 b)3 c)4 d)5 e)8</p>

<p>p408 #24 about the table and how many arrangements students can sit in.</p>

<p>p420 #23: The expression (3x-1)/4 + (x+6)/4 is how much more than x?</p>

<p>p431 #9 about teh rolling circle with radius 2/pie. this one is hard! I got B but its A. how'd u guys get that?</p>

<p>p465 #22 About naomi's jewery and #24 about integers j and k</p>

<p>p465 #25: The average of the test scores of a class of p students is 70, and the average of the test scores of a class of n students is 92. When the scores of both classes are combined, the average score is 86. What is teh value of p/n?</p>

<p>p470 #5: A certain scale for weighting food registers only weights above 6 pounds. A person who wanted to know the weight of 1 package each of chicken, beef, and turkey weighed eveyr possible pair of these packages and got the following results. </p>

<p>-the chicken and the beef weighed 7 pounds
-the chicken and turkey weighed 8 lbs
-the beef and turkey weighed 9 lbs
what is the weight of the package of turkey??<br>
i found out the answer by guess and check. Know any ways to solve using algebraic equations or a shortcut?????</p>

<p>p471 #7: The integer 33 is to be expressed as a sum of n consecutive positive integers. The value of n could be which of the following?
I. 2
II. 3
III. 6 </p>

<p>(a) I only (b) II only (c) I and II only (d) I and III only (e) I, II, and III
I figuered it out but it took like 3 minutes..any fast ways to do this type of prob?</p>

<p>p472 #9: If y=(5x^3)/z , what happens to the value of y when both x and z are doubled?
Answer is y is multiplied by 4. How'd u guys get this? I had no idea how to start!</p>

<p>Easy shortcuts and tricks are welcomed in any of these problems! THANKS!</p>

2

<p>Page 390 #3: It's just exponents.
2^6 = 64 > 50 = C</p>

<p>p390, #5.
Just use example numbers, since you know that they are (1) consecutive and (2) odd. Make e<f<g<h into e=1<f=3<g=5<h=7. g+h = 12 and e+f = 4. So (g+h) - (e+f) = 8 = e</p>

<p>I'm too tired to do the rest right now :( it seems like all i've done this summer is SAT stuff.</p>

3

<p>i have time to do one.</p>

<p>p465 #25: The average of the test scores of a class of p students is 70, and the average of the test scores of a class of n students is 92. When the scores of both classes are combined, the average score is 86. What is teh value of p/n?</p>

<hr>

<p>set up an equation
1) 70p+92n/p+n = 86<br>
p&n=how many students
2) cross multiply: 70p+92n = 86p+86n
3) simplify each side: 6n=16p or 3n=8p</p>

<p>divide&divide: p/n = 3/8</p>

4

<p>Thanks for the questions. I am so fu cking cheap that i still havn't bought practice tests after doing all the problems in the bluebook.</p>

<p>p420 #23: The expression (3x-1)/4 + (x+6)/4 is how much more than x?</p>

<p>(3x-1)/4 + (x+6)/4
(3x-1+x+6)/ 4
(4x+5)/4
4x/4 + 5/4
x + 5/4
answer is 5/4</p>

<p>**p470 #5: A certain scale for weighting food registers only weights above 6 pounds. A person who wanted to know the weight of 1 package each of chicken, beef, and turkey weighed eveyr possible pair of these packages and got the following results. </p>

<p>-the chicken and the beef weighed 7 pounds
-the chicken and turkey weighed 8 lbs
-the beef and turkey weighed 9 lbs
what is the weight of the package of turkey??
i found out the answer by guess and check. Know any ways to solve using algebraic equations or a shortcut?????**</p>

<p>you can use different letters to represent the different meats.
x can be chicken, y can be beef and z can be turkey. So</p>

<p>x+y=7
x+z=8
y+z=9</p>

<p>solve for x in the first equation:
x= 7-y</p>

<p>substitute that for x in the second equation:
(7-y)+ z= 8</p>

<p>solve for y in the third equation:
y= 9-z</p>

<p>substitute that into '(7-y)+ z= 8':
(7-9+z)+z = 8
solve---> 2z= 8+2
z= 5</p>

<p>there are several other ways to do subsitutions and solve for z.Eg. you can start with equation 2 instead of equation 1.</p>

<p>**p471 #7: The integer 33 is to be expressed as a sum of n consecutive positive integers. The value of n could be which of the following?
I. 2
II. 3
III. 6 </p>

<p>(a) I only (b) II only (c) I and II only (d) I and III only (e) I, II, and III
I figuered it out but it took like 3 minutes..any fast ways to do this type of prob?**</p>

<p>for two consecutive numbers you would use the equation
x+(x+1) = 33
x= 16</p>

<p>for three consecutive integers you would use
x+(x+1)+(x+2) = 33
x=10</p>

<p>for three consecutive integers you would use
x+(x+1)+(x+2)+(x+3)+(x+4)+(x+5) = 33
x=3</p>

<p>the reason i'm solving for x is to make sure that x is an integer for each of these cases. If x is an integer then the consecutive numbers are integers. So the answer must be E.</p>

<p>p472 #9: If y=(5x^3)/z , what happens to the value of y when both x and z are doubled?</p>

<p>just pick and use random numbers. like make x=2 and z=3. Ignore the 5.its a constant. So</p>

<p>(2)^3/ 3 = 2.6666
double both numbers---->(4)^3/ 6 = 10.6666
divide 10.6666 by 2.6666.</p>

5

<p>thanx for the answers,</p>

<p>but please answer number 24 on page 408, i've been dying to know how to do that one! if you don't have a book, heres the question: ok, so tehre's a diagram of a round table with 8 chairs around the table. the question says: the figure above represents a circular table with 8 equallly spaced chairs labeled 1 through 8. If two students are to sit directly opposite each other, leaving the other chairs empty, how many such arrangements of the two students are possible? </p>

<p>I'm confused between combinations and permutations. I know this question uses one of the above. Can someone explain to mee the difference between combs and permutes? and how I would do each of those? thanks.</p>

6

<p>DUDE, thanks for all the explanations....must've taken a while! =)</p>

7

<p>
[quote]
thanx for the answers,</p>

<p>but please answer number 24 on page 408, i've been dying to know how to do that one! if you don't have a book, heres the question: ok, so tehre's a diagram of a round table with 8 chairs around the table. the question says: the figure above represents a circular table with 8 equallly spaced chairs labeled 1 through 8. If two students are to sit directly opposite each other, leaving the other chairs empty, how many such arrangements of the two students are possible? </p>

<p>I'm confused between combinations and permutations. I know this question uses one of the above. Can someone explain to mee the difference between combs and permutes? and how I would do each of those? thanks.

[/quote]
</p>

<p>I'm pretty sure the answer is 8. You don't need to know permutations or combinations for this one. Just think about it. </p>

<p>Let the two students be A and B. Initially, there are four ways they can sit opposite each other (8 chairs, do the math). However, notice that A and B can switch so that A is where B originally was, which makes for another 4 ways. So that's a total of 8.</p>

<p>As for permutations and combinations, I'll let someone else explain that. In general you don't need them for SAT questions except for the rare occasion where a question bluntly poses a combination question that stresses the definition (which I can't remember at the moment but deals with selecting certain objects from a total where order does not matter).</p>

8

<p>Shortcut for p470 #5
c+b = 7
c+t = 8
b+t=9 Add the three equations
2(c+b+t) = 24 and c+b+t=12
subtract c+b = 7 from the last equation gives t=5</p>

<h1>24 Integers j/k</h1>

<p>we want to find integer k such that when 13 is divided by k, the remainder is 2. Note that 13 is a prime number, so when it is divided by any integer other than 13 or 1, it will have a unique remainder. So k must be 11. No other integer will yield a remainder of 2. </p>

<p><em>EDIT</em>
Rolling circle problem. Reading the question carefully, the FIRST time it touches is given and it is at 0. When A touches the line the second time, it has made a complete revolution and the distance it traveled is = to it's circumference. C=2(pi)r or 4 (since radius is 2/pi).</p>

<p>Hence the second time, it will touch 4, 3rd time- 8, 4th time- 12 (aka multiples of 4, or the circles circumference)</p>

<p>Finally, Naomi. The uncut disk is "a uniformly distributed 2.5 grams" One wedge is 40 deg or 1/9 of the disk (360 deg in a circle). So we simply dived 5/2 by 9 to get 5/18. </p>

<p>Hope this helps.</p>

9

<p>i agree with snipez- the simplest way to do this one would be to draw a circle and put eight dots around it. They probably wont give you a permuattion or combination problem that is so tough that the formulas cant be used. Just go to google and type, 'permutations,combinations and probabilities' and you'll get like 6 very good links that will explain how to do many of these kinds of problems.</p>

<p>snipet- thanks for the shortcut for no.5. I'll have to remember that.</p>