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What value of

satisfies both of the equations above?

The correct answer is1/2 or .5 Explanation Difficulty: Medium

Since

, the value of

is either

or

.

OR

The two values of Since

that satisfy the first equation are , the value of is either

and or .

.

OR

The two values of

that satisfy the second equation are

and

.

You are asked to find the value of The answer can be entered in the grid as

that satisfies both equations. That value is or .

.

ÏÂÃæÊÇÁ½µÀ SAT ÊýÑ§Á·Ï°Ìâ£¬¶¼ÊÇÑ¡ÔñÌâ£¬ºóÃæ¸½ÓÐ´ð°¸¼°Æä½âÎö¡£SAT ÊýÑ§Á·Ï°Ìâ¿ÉÒÔ ÈÃ´ó¼Ò¸ü¿ì¸üºÃµÄÁË½â SAT ÊýÑ§¿¼ÊÔµÄ³öÌâ·½Ê½ÒÔ¼°Ó¦¶Ô·½Ê½¡£ÏÂÃæÊÇÏêÏ¸ÄÚÈÝ£¬ÎÒÃÇÒ» ÆðÀ´¿´Ò»ÏÂÕâÐ© SAT ÊýÑ§Á·Ï°ÌâµÄ°É¡£ 1¡¢ Cone A has volume 24. When its radius and height are multiplied by the same factor, the cone¡¯s surface area doubles. What is Cone A¡¯s new volume? (A) (B)48

(C) (D)96 (E)Not enough information to tell 2¡¢ A rectangle stands so that its 6 inch side lies flat against the ground. If

the rectangle is rotated around the axis of one of its two 4 inch sides, what is the volume of the resulting cylinder? (A)24?€ (B)36?€ (C)64?€ (D)96?€ (D)144?€ Answers 1¡¢ C The formula for a cone¡®s surface area is ¦Ðr2 + ¦Ðrl. A cone¡®s volume is 1/ 3¦Ðr2h. So if the dimensions of a cone are multiplied by the same factor, a,

then its surface area multiplies by the square of that factor. If the dimensions of a cone are multiplied by the same factor, the volume becomes multiplied by the cube of that factor:

In general, for solids, if each dimension of a cone is multiplied by the same factor, the solid¡®s surface area is multiplied by the square of that factor, and its volume increases by the cube of that factor. If the surface area of Cone A doubles, its dimensions are multiplied by a factor of new volume is Thus, the cone¡®s volume is multiplied by a factor of Cone A¡®s

2¡¢ E If the rectangle is rotated about a side of length 4, then the height of the cylinder will be 4 and the radius will be 6.

Once you visualize the cylinder, you can plug in the values for the volume of a cylinder:

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ÏÂÃæÊÇÒ»µÀ¹ØÓÚÅ×ÎïÏßµÄ SAT ÊýÑ§Ìâ¼°Æä½â·¨µÄÄÚÈÝ£¬·Ç³£ÏêÏ¸¡£SAT ÌâÖÐ£¬Å×ÎïÏß ÊÇ±Ø¿¼µÄÒ»Àà£¬ËäÈ»ÖÐÑ§¿Î³Ì¶¼ÓÐËùÉæ¼°£¬»¹ÊÇÏà¶Ô±È½Ï³éÏó£¬ÓÈÆäÊÇÔÚÀí½â SAT ÊýÑ§Ìâ µÄ±í´ï·½Ê½ÉÏ¡£ÏÂÃæÎÒÃÇÀ´¿´¿´ÕâµÀ¹ØÓÚÅ×ÎïÏßµÄ SAT ÊýÑ§Ìâ°É¡£ Read the following SAT test question and then click on a button to select your answer.

The quadratic function values of

is graphed in the

-plane above. If ?

for all

, which of the following could be the coordinates of point

Answer Choices (A)

(B)

(C)

(D)

(E)

The correct answer is C Explanation The fact that for all values of means that the point is the

maximum of the quadratic function , so parabola intersects the between and -axis at the points

must be the vertex of the parabola. The and , so must be halfway

. Therefore, is . Therefore,

. Of the choices, the only one with could be the coordinates of

-coordinate equal to point .

1. What is the length of the line segment in the x-y plane with end points at (-2,-2) and (2,3)? A. 3 B. ¡Ì31 C. ¡Ì41 D. 7 E. 9

Correct Answer: C ½âÎö: Sketch a diagram and calculate the distance (hypotenuse of a right triangle) using Pythagoras theorem.

Vertical height of triangle = 5 ; horizontal side = 4 ; hypotenuse = ¡Ì(25 + 16) = ¡Ì41 2. n is an integer chosen at random from the set{5, 7, 9, 11 } p is chosen at random from the set{2, 6, 10, 14, 18} What is the probability that n + p = 23 ? A. 0.1 B. 0.2 C. 0.25 D. 0.3 E. 0.4 Correct Answer: A ½âÎö: Each of the integers in the first set could be combined with any from the second set, giving a total of 4 x 5 = 20 possible pairs. Of these the combinations that could give a sum of 23 are (5 + 18), and (9 + 14). This means that the probability of getting a sum of 23 is 2/20 = 1/10 3. A dress on sale in a shop is marked at $D. During the discount sale its price is reduced by 15%. Staff are allowed a further 10% reduction on the discounted price. If a staff member buys the dress what will she have to pay in terms of D ? A. 0.75D B. 0.76D C. 0.765D D. 0.775D

E. 0.805D Correct Answer: C ½âÎö: If the price is reduced by 15 %, then the new price will be 0.85D. If this new price is further reduced by 10%, the discounted price will be 0.9 x 0.85D = 0.765D

4. All the dots in the array are 2 units apart vertically and horizontally. What is the length of the longest line segment that can be drawn joining any two points in the array without passing through any other point ? A. 2 B. 2¡Ì2 C. 3 D. ¡Ì10 E. ¡Ì20 Correct Answer: E ½âÎö: The longest line segment that can be drawn without passing through any dots other than those at the beginning and end of the segment, such a line could go from the middle dot in the top row to either the bottom left or right dot. In any case the segment will be the hypotenuse of a right triangle with sides 2 and 4. Using Pythagoras theorem the hypotenuse will be ¡Ì(2 ? + 4 ? ) = ¡Ì20

5. If the radius of the circle with centre O is 7 and the measure of angle AOB is 100, what is the best approximation to the length of arc AB ? A. 9

B. 10 C. 11 D. 12 E. 13 Correct Answer: D ½âÎö: If the radius is 7, the circumference = 14¦Ð. The length of the arc is 100/360 of the circumference. Taking ¦Ð as 22/7 we get. (100 x 14 x 22) / (360 x 7) which reduces to 440/ 36 = 12.22 (i.e. approx. 12) 1¡¢At Central High School, the math club has members. If a total of members and the chess club has

students belong to only one of the two clubs, how many

students belong to both clubs? Answer Choices (A) (B) (C) (D) (E) The correct answer is C Explanation Let stand for the number of students who belong to both clubs. The members

of the math club can be broken down into two groups: those who are in both clubs (there are are The students in this category) and those who are in the math club only (there students in this category). members of the chess club can also be broken down into two groups: students who are in the chess club only.

students who are in both clubs and

Since a total of that belong to both clubs¡£ 2¡¢If numbers? Answer Choices (A) (B) (C) (D) (E)

students belong to only one of the two clubs, you know . Solving this equation gives , so students

is divisible by

,

, and

, which of the following is also divisible by these

The correct answer is D Explanation Since is divisible by , , , and , and , must be a multiple of are , , as , is the , ,

least common multiple of and .

. Some multiples of

If you add two multiples of example, of . If you add a multiple of be a multiple of sum, and

, the sum will also be a multiple of and their sum,

. For

are multiples of

, is also a multiple

to a number that is not a multiple of is a multiple of . , , and and

, the sum will not is not. Their

. For example,

, is not a multiple of

The question asks which answer choice is divisible by answer choice is a multiple of

; that is, which plus a

. All the answer choices are in the form of "

number." Only choice (D), and is also a multiple of 3¡¢In an alcohol is to . If

, has

added to a multiple of

. The sum of

, so the correct answer is choice (D).

solution of water and alcohol, the ratio by mass of water to grams of a solution consisting of grams water for each gram of

alcohol is added to the alcohol? Answer Choices

solution, what fraction by mass of the new solution is

(A)

(B)

(C)

(D)

(E) The correct answer is B Explanation To find what fraction by mass of the new solution is alcohol, you can find how many grams of alcohol are in the final solution of grams. Since the solution is

part alcohol to

parts water, it is

alcohol. So it contains

grams of alcohol. Similarly,

the

solution is

alcohol by mass, so it contains

grams of alcohol. Thus,

the final 20-gram solution contains

grams of alcohol, so

, or

, of it is alcohol.

1. Of the following, which is greater than ? A. 2/5

B. 4/7 C. 4/9 D. 5/11 E. 6/13 2. If an object travels at five feet per second, how many feet does it travel in one hour? A. 30 B. 300 C. 720 D. 1800 E. 18000 3. What is the average (arithmetic mean) of all the multiples of ten from 10 to 190 inclusive? A. 90 B. 95 C. 100 D. 105 E. 110 4. A cubical block of metal weighs 6 pounds. How much will another cube of the same metal weigh if its sides are twice as long? A. 48 B. 32 C. 24 D. 18 E. 12 5. In a class of 78 students 41 are taking French, 22 are taking German and 9 students are taking both French and German. How many students are not enrolled in either course? A. 6 B. 15 C. 24 D. 33 E. 54 1.Correct Answer: B Explanation: One way to deal with fractions is to convert them all to decimals. (Using your calculator, divide the numerator by the denominator).

In this case all you would need to do is to see which is greater than 0.5. Otherwise to see which is greater than ?, double the numerator and see if the result is greater than the denominator. In B, the correct answer, doubling the numerator gives us 8, which is bigger than 7. 2.Correct Answer: E Explanation: If an object travels at 5 feet per second it covers 5x60 feet in one minute, and 5x60x60 feet in one hour. Answer = 18000 (E) 3.Correct Answer: C Explanation: You could add up all the multiples of 10 (10 + 20 + 30 ....+190), and divide by the number of terms (19). Or you could realize that the average of an evenly spaced series of numbers is equal to the value of the middle term (or the average of the two middle terms if there are an even number of terms). The middle term out of 19 is the tenth term in the series = 100. 4.Correct Answer: A Explanation: If you double the sides of a cube, the ratio of the surface areas of the old and new cubes will be 1: 4. The ratio of the volumes of the old and new cubes will be 1: 8. Weight is proportional to volume. So, If the first weighs 6 pounds, the second weighs 6x8 pounds =48. 5.Correct Answer: C Explanation: You could solve this by drawing a Venn diagram. A simpler way is to realize that you can subtract the number of students taking both languages from the numbers taking French to find the number taking only French. Likewise find those taking only German. Then we have:Total = only French + only German + both + neither 78 = (41-9) + (22-9) + 9 + neither. Not enrolled students = 24 Á·Ï°Ò»ÏÂ°É£¬²»ÊÇºÜÄÑ¡£ 1. What is the sum of all the positive integer factors of 12 ? 2. The average IQ of 4 people is 110. If three people each have an IQ of 105, what is the IQ of the fourth person ? 3. Of 60 students in a class 2/3 are girls, and 2/5 of the class are taking music lessons. What is the maximum number of girls that are not taking music lessons? 4. If 2 n + 1 = 8, what is the value of n ?

5. In a certain game of 50 questions, the final score is calculated by subtracting twice the number of wrong answers from the total number of correct answers. If a player attempted all questions and received a final score of 35, how many wrong answers did he give?

6. Family 1 comprising mother, father and son are to be seated at a table with family 2 comprising mother, father and daughter. The layout of the table is shown in the diagram. F represents one of the fathers and M represents one of the mothers. X represents any family member but with the condition that a male family member must sit opposite a female of the other family. How many different seating plans are possible? 1. 145 300 610 1230 In the above sequence every term after the first is formed by multiplying by x and then adding y, where x and y are positive integers. What is the value of x + y? 2. A confectioner has 500 mint, 500 orange and 500 strawberry flavored sweets. He wishes to make packets containing 10 mint, 5 orange and 5 strawberry sweets. What is the maximum number of packets of this type he can make? 3. If S is the sum of 8,6,4,2 and x, what must be the value of x for x to equal 1/5 S ? 4. 25 per cent of 600 is equal to 15 per cent of what number? 5. What is the maximum number of points of intersection of four distinct lines in a plane? 6. If one edge of a 6-inch ruler is to be marked in 1/10 inch units, how many marks will there be on the edge including the 0 and 6 inch marks?

7. If the area of the right triangle above is 72, what is the value of x? 8. Given that the sum of the odd integers from 1 to 99 inclusive is 2500, what is the sum of the even integers from 2 to 100 inclusive? The projected sales volume of a video game cartridge is given by the

function

where

is the number of cartridges sold, in thousands; is a constant. If according to the

is

the price per cartridge, in dollars; and

projections, will be sold at

cartridges are sold at per cartridge?

per cartridge, how many cartridges

Answer Choices (A) (B) (C) (D) (E) The correct answer is C Explanation Difficulty: Medium For cartridges sold at per cartridge, (since is the

number of cartridges sold, in thousands) and yields

. Substituting into the equation

. Solving this equation for yields

.

Since

is a constant, the function can be written as

. To

determine how many cartridges will be sold at

per cartridge, you need to

evaluate be cartridges sold at

. Since per cartridge.

is given in thousands, there will

A special lottery is to be held to select the student who will live in the only deluxe room in a dormitory. There are seniors, juniors, and sophomores who applied. times; and

Each senior's name is placed in the lottery

times; each junior's name,

each sophomore's name, time. What is the probability that a senior's name will be chosen? Answer Choices

(A)

(B)

(C)

(D)

(E)

The correct answer is D Explanation Difficulty: Hard To determine the probability that a senior's name will be chosen, you must determine the total number of seniors' names that are in the lottery and divide this number by the total number of names in the lottery. Since each senior's name is placed in the lottery times, there are are seniors' names. Likewise, there juniors' names and sophomores' names in the

lottery. The probability that a senior's name will be chosen

is

.

Which of the following inequalities is graphed below?

(A)y > ¨C2x ¨C 2 (B)y ¡Ý ¨C2x ¨C 2 (C)y < ¨C2x ¨C 2 (D)y > x ¨C 2 (D)y > ¨C x ¨C 2 Correct Choice£ºA Explanation£º The slope of the line pictured is ¨C12?6 = ¨C2. The y-intercept of the line pictured is ¨C2. So the equation of the line pictured is y = ¨C2x ¨C 2. This leaves three choices. The line in the picture is dotted; this means that the inequality is either < or >, not ¡Ü or ¡Ý. Now we have two choices left. Because the region to the right and above is shaded, > is the correct inequality, but just to make sure, plug in a point or two. In this case, try the origin, (0,0). It is in the shaded region, and must therefore satisfy the inequality. Which inequality does is satisfy? It satisfies y > ¨C2x ¨C 2, so this is the correct choice. 1. The distance from town A to town B is five miles. C is six miles from B. Which of the following could be the distance from A to C? I 11 A. I only B. II only C. I and II only D. II and III only E. I, II, or III. Correct Answer: E ½âÎö: Do not assume that AB and C are on a straight line. Make a diagram with A and B marked 5 miles apart. Draw a circle centered on B, with radius 6. C could be anywhere on this circle. The minimum distance will be 1, and maximum 11, but anywhere in between is possible. 2. ¡Ì5 percent of 5¡Ì5 = A. 0.05 B. 0.25 C. 0.5 D. 2.5 E. 25 II 1 III 7

Correct Answer: B ½âÎö: We can write the statement mathematically, using x to mean ?of¡® and /100 for ?per cent¡®. So ( ¡Ì5/100) x 5¡Ì5 = 5 x 5 /100 = 0.25 3. If pqr = 1 , rst = 0 , and spr = 0, which of the following must be zero? A. P B. Q C. R D. S E. T Correct Answer: D ½âÎö: 4.If pqr = 1, none of these variable can be zero. Since spr = 0 , and since p and r are not zero, s must be zero. (Note that although rst = 0, and so either s or t must be zero, this is not sufficient to state which must be zero) A. 1/5 B. 6/5 C. 63 D. 64 / 5 E. 64 Correct Answer: E ½âÎö: 65 = 64x 6 (64 x 6) - 64 = 64(6 - 1) = 64 x 5 Now, dividing by 5 will give us 64 5. -20 , -16 , -12 , -8 .... In the sequence above, each term after the first is 4 greater than the preceding term. Which of the following could not be a term in the sequence? A. 0 B. 200 C. 440 D. 668 E. 762 Correct Answer: E ½âÎö: All terms in the sequence will be multiples of 4. 762 is not a multiple of 4¡£ Mathematics > Standard Multiple Choice

Read the following SAT test question and then click on a button to select your answer. If the length and width of rectangle are percent less and , the area of percent less, is equal to what

respectively, than the length and width of rectangle percent of the area of Answer Choices (A) ?

(B)

(C)

(D)

(E)

The correct answer is A Explanation Let Then rectangle and represent the length and width, respectively, of rectangle and . Simplifying .

represent the length and width, respectively, of and gives and is for . The

the length and width, respectively, of rectangle area of rectangle rectangle is is , or

. The area of rectangle

. Therefore, the area of

percent of the area of rectangle

ÏÂÃæÎª´ó¼ÒÌá¹©Ò»Ð©ºÍÕâÐ© SAT ¹Ù·½Ã¿ÈÕÒ»ÌâÏàËÆµÄÌâÄ¿£¬¹©´ó¼ÒÁ·Ï°£º

In the xy-coordinate (×ø±ê) plane above, the line contains the points (0,0) and (1,2). If line M (not shown) contains the point (0,0) and is perpendicular £¨´¹Ö±£© to L, what is an equation of M? (A) y = -1/2 x (B) y = -1/2 x + 1 (C) y = - x (D) y = - x + 2 (E) y = -2x ´ð°¸£º (E) Read the following SAT test question, then click on a button to select your answer. What is the area of the triangle in the figure above?

A.4.0 B.7.5 C.8.0 D.8.5 E.15.0 ´ð°¸ºÍ½âÎö Correct Answer: B Here's Why: Figures in a Coordinate Plane The figure provides all the information you need to answer the question. What Is the Question Asking? You are asked to figure out the area of a triangle that is defined by the points in a coordinate plane. What Do You Know? The triangle in the figure is a right triangle with the right angle at the lower left. Because it is a right triangle, its base and height are the two sides that form the right angle. The area of a triangle isbh.

The base of the triangle extends from point (0, 0) to point (5, 0). So it is 5 units long. The height of the triangle extends from point (0, 0) to point (0, 3). So it is 3 units long. Area =bh=(3)(5)= (15)= 7.5 Difficulty: Medium Question Type: Standard Multiple Choice 1. If 10+x is 5 more than 10, what is the value of 2x ? (A)-5 (B) 5 (C) 10 (D) 25 (E) 50 2. If(x -2)2 =49, then x could be (A) -9 (B) -7 (C) 2 (D) 5 (E) 9 3. If this page was folded along the dotted line in the figure above, the left half of the letter W would exactly coincide with the right half of W. Which of the following letters, as shown, CANNOT be folded along a vertical line so that its left half would coincide with its right half? (A) A (B) I (C) O (D) U (E) E 4. In a certain store, the regular price of a refrigerator is $600. How much money is saved by buying this refrigerator at 20 percent off the regular price rather than buying it on sale at 10 percent off the regular price with an additional discount of 10 percent off the sale price? (A) $6 (B) $12 (C) $24 (D) $54 (E) $60 5. Based on the portions of the graphs of the functions f and g shown above, what are all values of x between -6 and 6 for which g x f x ? (A) -6 < x <-3 only (B) -3 < x < 0 only (C) 0 < x < 3 only (D) 3 < x < 6 only (E) -6 < x < -3 and 0 < x < 3¡£ 6. Point O is the center of both circles in the figure above. If the circumference of the large circle is 36 and the radius of the small circle is half of the radius of the large circle, what is the length of the darkened arc? (A) 10 (B) 8 (C) 6 (D) 4 (E) 2 7. If x = 20 and y = 30 in the figure above, what is the value of z ? (A) 60 (B) 70 (C) 80 (D) 90 (E) 100 8. If 6 < |x-3| < 7 and x < 0, what is one possible value of |x| ? 9. What is the product of the smallest prime number that is greater than 50 and the greatest prime number that is less than 50 ? ´ð°¸ 1.(C)£¬ 2. (E)£¬ 3. (E)£¬ 4.(A)£¬ 5.( (B)£¬ 6. (D)£¬ 7. (B)£¬ 8.x < 4, 9.1300 The circle shown above has center O and a radius of length 5. If the area of the shaded region is 20 , what is the value of x? A. 18

B. 36 C. 45 D. 54 E. 72

What is the area of the triangle in the figure above? A.4.0 B.7.5 C.8.0 D.8.5 E.15.0 Àý 1 £º At a certain diner, Joe orders 3 doughnuts and a cup of coffee and is charged $2.25. Stella orders 2 doughnuts and a cup of coffee and is charged $1.70. What is the price of 2 doughnuts?

(A) $ 0.55 (B) $ 0.60 (C) $ 1.10 (D) $ 1.30 (E) $ 1.80 °´ÕÕ³£¹æµÄ½âÌâË¼Â·£¬ÎÒÃÇ¿ÉÒÔÓÃ×ÖÄ¸¨D d ¡¬ºÍ¨D c ¡¬·Ö±ðÖ¸´ú¨DÕ¨Ãæ°üÈ¦¡¬ºÍ¨D¿§·È¡¬µÄ¼Û¸ñ£¬ È»ºóÁªÁ¢ 2 ¸ö·½³ÌÊ½( 3 ¡Á d + c = $ 2.25 ¡¢ 2 ¡Á d + c = $ 1.70 )£¬×îºóÇó³ö·½³Ì×éµÄ½â( d = $ 0.55 ¡¢ c = $ 0.6 )¡£ µ«ÊÇÖ»ÒªÉÔ×÷Ë¼¿¼£¬ ÎÒÃÇ²»ÄÑ·¢ÏÖ½âÌâµÄ½Ý¾¶¡ª¡ª 3 ¸öÕ¨Ãæ°üÈ¦¼Ó 1 ±¿§·ÈµÄ¼Û¸ñÓë

2 ¸öÕ¨Ãæ°üÈ¦¼Ó 1 ±¿§·ÈµÄ¼Û¸ñÏà¼õ£¬Óà¶î¾ÍÊÇ 1 ¸öÕ¨Ãæ°üÈ¦µÄ¼Û¸ñ£º $ 2.25 - $ 1.70 = $ 0.55 ¡£´ËÊ±£¬ÎÒÃÇ»¹Òª×¢ÒâµÄÊÇ¡ª¡ªÇ§Íò²»ÄÜµôÈëÃüÌâÕßµÄÏÝÚå¶øÑ¡Ôñ A !ÒòÎª A Ñ¡Ïî Ö»ÊÇ 1 ¸öÕ¨Ãæ°üÈ¦µÄ¼Û¸ñ¡£ËùÒÔ£¬ÕýÈ·´ð°¸Ó¦¸ÃÊÇ C Ñ¡Ïî¡£

1. If 10+x is 5 more than 10, what is the value of 2x ? (A)-5 (B) 5 (C) 10 (D) 25 (E) 50

2. If(x -2)2 =49, then x could be (A) -9 (B) -7 (C) 2 (D) 5 (E) 9

3. If this page was folded along the dotted line in the figure above, the left half of the letter W would exactly coincide with the right half of W. Which of the following letters, as shown, CANNOT be folded along a vertical line so that its left half would coincide with its right half? (A) A (B) I (C) O (D) U (E) E

4. In a certain store, the regular price of a refrigerator is $600. How much money is saved by buying this refrigerator at 20 percent off the regular price rather than buying it on sale at 10 percent off the regular price with an additional discount of 10 percent off the sale price? (A) $6 (B) $12 (C) $24 (D) $54 (E) $60

5. Which of the following is the graph of a function f such that f(x) = 0 for exactly two values of x between -5 and 5 ? (A) (C) (E) 6. Based on the portions of the graphs of the functions f and g shown above, what are all values of x between -6 and 6 for which g x f x ? (A) -6 < x <-3 only (D) 3 < x < 6 only (B) -3 < x < 0 only (C) 0 < x < 3 only (B) (D)

(E) -6 < x < -3 and 0 < x < 3¡£

7. Point O is the center of both circles in the figure above. If the circumference of the large circle is 36 and the radius of the small circle is half of the radius of the large circle, what is the length of the darkened arc? (A) 10 (B) 8 (C) 6 (D) 4 (E) 2

8. If x = 20 and y = 30 in the figure above, what is the value of z ? (A) 60 (B) 70 (C) 80 (D) 90 (E) 100

9. If 6 < |x-3| < 7 and x < 0, what is one possible value of |x| ? 10. What is the product of the smallest prime number that is greater than 50 and the greatest prime number that is less than 50 ? 2.´ð°¸ 1.(C)£¬ 2. (E)£¬ 3. (E)£¬ 4.(A)£¬ 5.(D)£¬ 6. (B)£¬ 7. (D)£¬ 8. (B)£¬ 9.x < 4, 10.1300

Àý 2 £º If n Velcro tabs cost p dollars, then how many dollars would q Velcro tabs cost? (A) np/q (B) nq/p (C) pq/n (D) n/pq

(E) p/nq ÎÒÃÇ¿ÉÒÔÉè n £½ 2 £¬ p £½ 4 £¬ q £½ 3 ¡£ÔÎÊÌâ¾Í±äÎª¡ª¡ª¨D If 2 Velcro tabs cost $ 4, then how many dollars would 3 Velcro tabs cost? ¡¬ºÜÈÝÒ×µÃ³ö´ð°¸ÊÇ $ 6 ¡£È»ºó¿¼ÉúÖ»Ðè °Ñ¾ßÌåÊý×Ö´úÈë¸÷Ñ¡ÏîÖÐ£¬¿´ÄÄ¸öÑ¡Ïî¿ÉÒÔµÃ³ö 6 £¬¼´µÃÕýÈ·´ð°¸Îª C ¡£ Averages are a statistics that are used to get information on a set of data. The arithmetic mean of a set of n numbers is equal to the sum of the numbers divided by n. SAT math questions that use the word average refer to the arithmetic mean. For example, the arithmetic mean of 4, 5 and 9 will be (4 + 5 + 9)/3 = 6. Example of SAT question using the arithmetic mean: The average of the integers 24, 6, 12, x and y is 11. What is the value of the sum x + y? (a) 11 (b) 17 (c) 13 (d) 15

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Answer: The average of the 5 numbers is (24 + 6 + 12 + x + y)/5. This should be equal to 11 according to the problem, so 24 + 6 + 12 + x + y = 11 ¡¤5 = 55 x + y = 55 - 24 - 6 - 12 = 13

The median of a set of numbers is the number in the middle when the numbers are ordered. For example, the median of (1, 5, 2, 7, and 10) is 5 because when the numbers are ordered, 5 is in the middle. When there is an even number of values, the median is the same as the mean of the two middle numbers. The mode of a set of numbers is the number that occurs most often in the list. For example, 75 is the mode of 24, 75, 55, 84, 75, and 12. A list of numbers can have more than one mode, for example (22, 24, 22, 25, 24, 27, 27, 29) has 3 modes, 22, 24 and 27. Example of SAT question using statistics: A parameter is measured during a scientific experiment and the results are -12, 4, -8, 10, 2, 2, 0, -4 and 2. The median and the average of these numbers are: (a) median = 0, average = -4/9 (b) median = 0, average = 4/9 (c) median = 2, average = -4/9 (d) median = 2, average = 4/9 (e) median = 2, average = 2/9

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Answer: You may arrange the numbers in order: -12, -8, -4, 0, 2, 2, 2, 4, and 10. The median will be number in the middle of the row, that is 2 The average will be (-12-8-4+0+2+2+2+4+10)/9 = -4/9. The correct answer is (c)

Probability is the likelihood or chance that something is the case or will happen. A probability may be expressed as either a decimal or a fraction. If the probability is 0, the event can never occur and if the probability is 1 the event is certain to occur. If the probability is between 0 and 1, that number expresses the likelihood of occurrence. Example of SAT exercise with probability: If a is an integer chosen randomly from the set {3, 4, 5, 9} and b is an integer chosen randomly from the set {3, 8, 12, 15}, what is the probability that a/b is an integer? (a) .25 (b) .2 (c) .125 (d) .375 (e) .4

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Answer: We have 4 possible integers for a and 4 for b, so the number of possible combinations for (a / b) is 16 a/b is an integer only for 2 combinations: 1. a = 3 and b = 3 1. a = 9 and b = 3 The probability that a/b is an integer is 2/16 = 1/8 = .125. (c) is the correct answer.

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