THE SAT MATH SECTION 13 ppt

13. Given the following: Set A is the set of prime integers. Set B is the set of positive odd integers. Set C is the set of positive even integers. Which of the following are true? I. Set A | Set C yields Ø. II. Set A | Set B contains more elements than Set A | Set C. III. Set B | Set C yields Ø. a. I only b. II and III only c. II only d. III only e. I and III only 14. Line l has the equation 3x – y = 8. What is the y-intercept of line l? a. (8,0) b. (0,8) c. (–8,–8) d. (0,–8) e. (–8,0) 15. In the triangle below, what is the length of the hypotenuse, h? a. 12.5͙3 ෆ b. c. 25 d. 25͙3 ෆ e. 25͙3 ෆ ᎏ 3 12.5͙3 ෆ ᎏ 3 30 o 12.5 h –THE SAT MATH SECTION– 105 5658 SAT2006[04](fin).qx 11/21/05 6:44 PM Page 105 Grid-in Questions For the next 15 questions, solve the problem and enter your solution into the grid by marking the ovals, as shown below. ■ The answer sheets are scored by a machine, so regardless of what else is written on the answer sheet, you will only receive credit if you have filled in the ovals correctly. ■ Be sure to mark only one oval in each column. ■ You may find it helpful to write your answer in the boxes on top of the columns. ■ If you find that a problem has more than one correct answer, grid only one answer. ■ None of the grid-in questions will have a negative number as a solution. ■ Mixed numbers like 1 ᎏ 1 3 ᎏ must be entered as 1.3333 or ᎏ 4 3 ᎏ . (If the response is “gridded” as ᎏ 1 3 1 ᎏ , it will be read as ᎏ 1 3 1 ᎏ , not 1 ᎏ 1 3 ᎏ .) ■ If your answer is a decimal, use the most accurate value that can be entered into the grid. For example, if your solution is 0.333 ,your “gridded” answer should be .333. A less precise answer, like .3 or .33, will be scored as an incorrect response. 1 2 3 4 5 6 7 8 9 • 2 3 4 5 6 7 8 9 0 • / 1 2 3 4 5 6 7 8 9 0 • 1 2 4 5 6 7 8 9 0 • 1 2 3 4 5 6 7 8 9 1 2 4 5 6 7 8 9 0 • / 1 2 4 5 6 7 8 9 0 • / 1 2 4 5 6 7 8 9 0 • 1/3 .333 These are both acceptable ways to grid = 0.333. 1 3 1 2 3 5 6 7 8 9 • 1 2 3 4 5 6 7 8 9 0 • 1 2 4 5 6 7 8 9 0 • / 1 2 3 4 5 6 7 8 9 0 • 2 3 4 5 6 7 8 9 • 1 2 3 4 5 6 7 8 9 0 / 1 2 3 5 6 7 8 9 0 • / 1 2 3 4 5 6 8 9 0 • 4/3 1.47 Note: You may start your answers in any of the columns, as long as there is space. Answer: Answer: 1.47 4 3 –THE SAT MATH SECTION– 106 5658 SAT2006[04](fin).qx 11/21/05 6:44 PM Page 106 16. A wealthy businessperson bought charity auction tickets that were numbered consecutively, 5,027 through 5,085. How many tickets did she purchase? 17. For some value of x,5(x + 2) = y. After the value of x is increased by 3, 5(x + 2) = z. What is the value of z – y? 18. When a positive integer k is divided by 6, the remainder is 3. What is the remainder when 5k is divided by 3? 19. If (x – 1)(x – 3) = –1, what is a possible solution for x? 20. If 4 times an integer x is increased by 10, the result is always greater than 18 and less than 34. What is the least value of x? 21. A string is cut into two pieces that have lengths in the ratio 4:5. If the length of the string is 45 inches, what is the length of the longer string? 22. If x – 8 is 4 greater than y + 2, then by how much is x + 12 greater than y? 23. A brand of paint costs $14 a gallon, and 1 gallon of paint will cover an area of 150 square feet. What is the minimum cost of paint needed to cover the 4 walls of a rectangular room that is 12 feet wide, 16 feet long, and 8 feet high? 24. How many degrees does the minute hand of a clock move from 5:25 p.m. to 5:47 p.m. of the same day? 25. If the operation ∇ is defined by the equation x∇y = 3x + 3y, what is the value of 3∇4? 26. What is the value of s below? = When multiplying two 2 × 2 matrices, use the formulas: × = 27. If x 5 = 243, what is the value of x –3 ? 28. In the diagram below, AB ៮ is tangent to circle C at point B. What is the radius of circle C if AC ៮ is 20? 29. Given f(x) = 3x 2 + 2 –x + ᎏ 3 8 ᎏ , find f(3). 30. For the portion of the graph shown, for how many values of x does f(x) = 0? x y 1234567 1 2 3 4 5 –1 –2 –3 –1–2–3–4–5–6–7 A B C 16 [ a 1 b 1 + a 2 b 3 a 1 b 2 + a 2 b 4 ] a 3 b 1 + a 4 b 3 a 3 b 2 + a 4 b 4 [ b 1 b 2 ] b 3 b 4 [ a 1 a 2 ] a 3 a 4 [ qr ] st [ 1 8 ] 2 1 [ 5 8 ] 4 1 –THE SAT MATH SECTION– 107 5658 SAT2006[04](fin).qx 11/21/05 6:44 PM Page 107  Math Pretest Answers 1. b. To figure out by what amount quantity A exceeds quantity B, calculate A – B: (8 × 25) – (15 × 10) = 200 – 150 = 50. 2. d. Consecutive multiples of 4, such as 4, 8, and 12, always differ by 4. If k – 1 is a multiple of 4, then the next larger multiple of 4 is obtained by adding 4 to k – 1, which gives k – 1 + 4 or k + 3. 3. d. Since 2 x + 1 = 32 and 32 = 2 5 , then 2 x + 1 = 2 5 . Therefore, x + 1 = 5, so (x + 1) 2 = 5 2 = 25. 4. c. If (x + 7)(x – 3) = 0, then either or both fac- tors may be equal to 0. If x + 7 = 0, then x = –7. Also, if x – 3 = 0, then x = 3. Therefore, x may be equal to –7 or 3. 5. d. The phrase “3 less than 2 times x” means 2x minus 3 or 2x – 3. 6. c. When the recipe is adjusted from 4 to 8 serv- ings, the amounts of salt and pepper are each doubled; however, the ratio of 2:3 remains the same. 7. d. In a triangle, the length of any side is less than the sum of the lengths of the other two sides. If the lengths of two sides are 5 and 9, and the length of the third side is x, then ■ x < 5 + 9 or x < 14 ■ 5 < x + 9 ■ 9 < x + 5 or 4 < x Since x < 14 and 4 < x,4 < x < 14. 8. c. If the circumference of a circle is 10π, its diameter is 10 and its radius is 5. Therefore, its area is π(5 2 ) = 25π. 9. a. The total number of different sundaes that the ice cream parlor can make is the number of different flavors of ice cream times the number of different flavors of syrup times the number of different toppings: 6 × 3 × 4 = 72. 10. b. Following the given rule for the sequence up to and including 55: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55. Since 10 numbers are listed, n = 10. 11. d. Notice that: term 1 = 9 term 2 = 9 × 5 1 term 3 = 9 × 5 2 term 4 = 9 × 5 3 This question asks you for the eighth term, so you know that term 8 must equal 9 × 5 7 = 9 × 78,125 = 703,125. 12. c. The area of the big circle is πr 2 = 64π, and the area of the shaded circle is πr 2 = 4π.So, the probability of hitting the shaded part is 4π out of 64π, which reduces to 1 out of 16. 13. b. The symbol | means intersection. Consider Set A | Set C. This yields positive integers that are both prime and even. There is only one such positive integer: 2. Statement I is not true because the intersection of the two sets does not yield the empty set (Ø). Now consider statement II. We already saw that Set A | Set C contains one element. Set A | Set B contains all positive integers that are prime and odd, such as 3, 5, 7, and so on. Set A | Set B does contain more elements than Set A | Set C, so statement II is true. Set B | Set C does yield Ø, so statement III is true. Thus, the correct answer is b. 14. d. Rearrange the given equation into the form y = mx + b, and use the value of b to find the y value of the (x,y) coordinates of the inter- cept; 3x – y = 8 becomes 3x – 8 = y, which is equivalent to y = 3x – 8. Thus, b = –8. The y-intercept is then (0,–8). 15. c. Recall that cos θ = ᎏ H A yp d o ja t c e e n n u t se ᎏ . Using the knowledge that cos 60 = ᎏ 1 2 ᎏ , we know that h is equal to 12.5 × 2, or 25. 16. 59. If A and B are positive integers, then the number of integers from A to B is (A – B) + 1. Therefore, the number of tickets is equal to (5,085 – 5,027) + 1 = 59. –THE SAT MATH SECTION– 108 5658 SAT2006[04](fin).qx 11/21/05 6:44 PM Page 108 17. 15. If the value of x is increased by 3, then the value of y is increased by 15. After x is increased by 3, 5(x + 2) = z. Therefore, the value of z – y = 15. 18. 0. When k is divided by 6, the remainder is 3, so let k = 9. Then 5k = 45 and 45 is divided evenly by 3. Therefore, the remainder is 0. 19. 2. If (x – 1)( x – 3) = –1, then x 2 – 4x + 3 = –1, and therefore, x 2 – 4x + 4 = 0. After factor- ing, this equation results in (x – 2)(x – 2) = 0. Hence, a possible value is 2. 20. 3. This problem can be written as 18 < 4x + 10 < 34. Subtracting 10 from both sides gives the equation 8 < 4x < 24. Dividing by 4 will result in the following: 2 < x < 6. Since 2 is less than x, the least integer value for x is 3. 21. 25. Since the lengths of the two pieces of string are in the ratio 4:5, let 4x and 5x represent their lengths. Therefore, 4x + 5x = 45, 9x = 45, and x = 5. Hence, the longest piece of string is (5)(5) = 25. 22. 26. If x – 8 is 4 greater than y + 2, then x – 8 = y + 2 + 4. x – 8 = y + 6 x = y + 14 Since x + 12 = (y + 14) + 12 = y + 26, then x + 12 is 26 greater than y. 23. 42. First, find the sum of the areas of the four walls: 2(12 × 8) + 2(16 × 8) = 448. Since 1 gallon of paint provides coverage of an area 150 square feet, simply divide 448 by 150, which results in 2.986 ෆ , meaning a minimum of 3 gallons of paint is needed. Since the paint costs $14 a gallon, to find the cost of the paint, simply multiply 14 by 3 = $42. 24. 132. From 5:25 p.m. to 5:47 p.m., the minute hand moves 22 minutes. Since there are 60 minutes in one hour, 22 minutes represents ᎏ 2 6 2 0 ᎏ of the clock circle. Because there are 360 degrees in a circle, multiply ᎏ 2 6 2 0 ᎏ by 360, or 22 × 6, to get 132. 25. 21. Since x∇y = 3x + 3y, then 3∇4 = 3(3) + 3(4) = 9 + 12 = 21. 26. 6. To find the value of s, we use the formula that corresponds to the position of s. The formula is a 3 b 1 + a 3 b 4 = (4)(1) + (1)(2) = 4 + 2 = 6. 27. ᎏ 2 1 7 ᎏ . 243 = 3 × 3 × 3 × 3 × 3. Since 3 5 = 243, x is equal to 3. Next, find 3 –3 = ᎏ 3 1 3 ᎏ = ᎏ 2 1 7 ᎏ . 28. 12. Since AB ៮ is tangent to circle C at point B,we know (by definition) that it is perpendicular to the radius of the circle. The radius is BC ៮ . By constructing a right triangle with sides AB ៮ , AC ៮ , and BC ៮ , we can use a Pythagorean triplet to solve for BC ៮ (the radius). Using the double of the Pythagorean triplet 6-8-10 (6 2 + 8 2 = 10 2 ), we can see that we have a 12-16-20 right triangle. The radius, BC ៮ , is 12. Note that the popular Pythagorean triplets are 3-4-5, 6-8-10, and 5-12-13. 29. 27.5. Substitute 3 for x in the function f(x) = 3x 2 + 2 –x + ᎏ 3 8 ᎏ to get f(3) = 3(3) 2 + 2 –3 + ᎏ 3 8 ᎏ = 3(9) + ᎏ 2 1 3 ᎏ + ᎏ 3 8 ᎏ = 27 + ᎏ 1 8 ᎏ + ᎏ 3 8 ᎏ = 27 + ᎏ 4 8 ᎏ = 27.5. 30. 3. For the portion of the graph shown, there are three values of x where f(x) = 0. x y 1234567 1 2 3 4 5 –1 –2 –3 –1–2–3–4–5–6–7 A B C 16 20 –THE SAT MATH SECTION– 109 5658 SAT2006[04](fin).qx 11/21/05 6:44 PM Page 109  Arithmetic Review Numbers All of the numbers you will encounter on the SAT are real numbers: ■ Whole numbers—Whole numbers are also known as counting numbers: 0, 1, 2, 3, 4, 5, 6, ■ Integers—Integers are both positive and negative whole numbers including zero: 3,–2,–1,0,1, 2,3, ■ Rational numbers—Rational numbers are all numbers that can be written as fractions ( ᎏ 2 3 ᎏ ), ter- minating decimals (.75), and repeating decimals .6 ෆ 6 ෆ 6 ෆ ■ Irrational numbers—Irrational numbers are numbers that cannot be expressed as terminating or repeating decimals: π or ͙2 ෆ . Comparison Symbols The following table will illustrate the different com- parison symbols on the SAT. = is equal to 5 = 5 ≠ is not equal to 4 ≠ 3 > is greater than 5 > 3 ≥ is greater than or equal to x ≥ 5 (x can be 5 or any number > 5) < is less than 4 < 6 ≤ is less than or equal to x ≤ 3 (x can be 3 or any number < 3) Symbols of Multiplication When two or more numbers are being multiplied, they are called factors. The answer that results is called the product. Example: 5 × 6 = 30 5 and 6 are factors and 30 is the product. There are several ways to represent multiplication in the above mathematical statement. ■ A dot between factors indicates multiplication: 5 • 6 = 30 ■ Parentheses around any part of the one or more factors indicates multiplication: (5)6 = 30, 5(6) = 30, and (5)(6) = 30 ■ Multiplication is also indicated when a number is placed next to a variable: 5a = 30 In this equation, 5 is being multiplied by a. Like Terms A variable is a letter that represents an unknown num- ber. Variables are frequently used in equations, formu- las, and mathematical rules to help you understand how numbers behave. When a number is placed next to a variable, indi- cating multiplication, the number is said to be the coefficient of the variable. Example: 8c 8 is the coefficient to the variable c. 6ab 6 is the coefficient to both variables, a and b. If two or more terms have exactly the same vari- able(s), they are said to be like terms. –THE SAT MATH SECTION– 110 5658 SAT2006[04](fin).qx 11/21/05 6:44 PM Page 110 Example: 7x + 3x = 10x The process of grouping like terms together performing mathematical operations is called combining like terms. It is important to combine like terms carefully, making sure that the variables are exactly the same. This is especially important when working with exponents. Example: 7x 3 y + 8xy 3 These are not like terms because x 3 y is not the same as xy 3 . In the first term, the x is cubed, and in the sec- ond term, it is the y that is cubed. Because the two terms differ in more than just their coefficients, they cannot be combined as like terms. This expression remains in its simplest form as it is written. Laws of Arithmetic Listed below are several “math laws,” or properties. Just think of them as basic rules that you can use as tools when solving problems on the SAT exam. ■ Commutative Property. This law enables you to change the order of numbers being either multi- plied or added. Examples: 5 × 2 = 2 × 5 5a = a5 ■ Associative Property. This law states that paren- theses can be moved to group numbers differently when adding or multiplying. Examples: 2 × (3 × 4) = (2 × 3) × 42(ab) = (2a)b ■ Distributive Property. When a value is being multiplied by a quantity in parentheses, you can multiply that value by each variable or number within the parenthesis and then take the sum. Example: 5(a + b) = 5a + 5b This can be proven by doing the math: 5(1 + 2) = (5 × 1) + (5 × 2) 5(3) = 5 + 10 15 = 15 Order of Operations There is an order for doing every mathematical oper- ation. That order is illustrated by the following acronym: Please Excuse My Dear Aunt Sally. Here is what it means mathematically: P: Parentheses. Perform all operations within parentheses first. E: Exponents. Evaluate exponents. M/D: Multiply/Divide. Work from left to right in your division. A/S: Add/Subtract. Work from left to right in your subtraction. Example: 5 + [ ] = 5 + [ ] = 5 + ᎏ 2 1 0 ᎏ = 5 + 20 = 25 Powers and Roots Exponents An exponent tells you how many times the number, called the base, is a factor in the product. Example: 2 5-exponent = 2 × 2 × 2 × 2 × 2 = 32 ⇑ base 20 ᎏ (1) 2 20 ᎏ (3 – 2) 2 –THE SAT MATH SECTION– 111 5658 SAT2006[04](fin).qx 11/21/05 6:44 PM Page 111 Sometimes, you will see an exponent with a vari- able: b n . The “b”represents a number that will be a fac- tor to itself “n” times. Example: b n where b = 5 and n = 3 Don’t let the variables fool you. Most expressions are very easy once you substi- tute in numbers. b n = 5 3 = 5 × 5 × 5 = 125 Laws of Exponents ■ Any base to the zero power is always 1. Examples: 5 0 = 1 70 0 = 1 29,874 0 = 1 ■ When multiplying identical bases, you add the exponents. Examples: 2 2 × 2 4 × 2 6 = 2 12 a 2 × a 3 × a 5 = a 10 ■ When dividing identical bases, you subtract the exponents. Examples: ᎏ 2 2 5 3 ᎏ = 2 2 ᎏ a a 7 4 ᎏ = a 3 Here is another method of illustrating multipli- cation and division of exponents: b m × b n = b m + n ᎏ b b m n ᎏ = b m – n ■ If an exponent appears outside of the parentheses, you multiply the exponents together. Examples: (3 3 ) 7 = 3 21 (g 4 ) 3 = g 12 Squares and Square Roots The square root of a number is the product of a num- ber and itself. For example, in the expression 3 2 = 3 × 3 = 9, the number 9 is the square of the number 3. If we reverse the process, we can say that the number 3 is the square root of the number 9. The symbol for square root is ͙25 ෆ and it is called the radical. The number inside of the radical is called the radicand. Example: 5 2 = 25; therefore, ͙25 ෆ = 5 Since 25 is the square of 5, we also know that 5 is the square root of 25. Perfect Squares The square root of a number might not be a whole number. For example, the square root of 7 is 2.645751311 It is not possible to find a whole number that can be multiplied by itself to equal 7. A whole number is a perfect square if its square root is also a whole number. Examples of perfect squares: 1,4,9,16,36,49,64,81,100, Properties of Square Root Radicals ■ The product of the square roots of two numbers is the same as the square root of their product. Example: ͙a ෆ × ͙b ෆ = ͙a × b ෆ ͙5 ෆ × ͙3 ෆ = ͙15ෆ ■ The quotient of the square roots of two numbers is the square root of the quotient. Example: ■ The square of a square root radical is the radicand. Example: (͙N ෆ ) 2 = N (͙3 ෆ ) 2 = ͙3 ෆ × ͙3 ෆ = ͙9 ෆ = 3 √ ¯¯¯ √ ¯¯¯ a √ ¯¯¯ b √ ¯¯ ¯ 5 = = a b (b ≠ 0) √ ¯¯¯¯¯ 15 √ ¯¯¯ 3 √ ¯¯¯¯¯ 15 3 = –THE SAT MATH SECTION– 112 5658 SAT2006[04](fin).qx 11/21/05 6:44 PM Page 112 ■ To combine square root radicals with the same radicands, combine their coefficients and keep the same radical factor. You may add or subtract radicals with the same radicand. Example: a͙b ෆ + c͙b ෆ = (a + c)͙b ෆ 4͙3 ෆ + 2͙3 ෆ = 6͙3 ෆ ■ Radicals cannot be combined using addition and subtraction. Example: ͙a + b ෆ ≠ ͙a ෆ + ͙b ෆ ͙4 + 11 ෆ ≠ ͙4 ෆ + ͙11 ෆ ■ To simplify a square root radical, write the radi- cand as the product of two factors, with one num- ber being the largest perfect square factor. Then write the radical over each factor and simplify. Example: ͙8 ෆ = ͙4 ෆ × ͙2 ෆ = 2͙2 ෆ Integer and Rational Exponents Integer Exponents When dealing with negative exponents, remember that a –n = ᎏ a 1 n ᎏ . Examples: 4 –2 = ᎏ 4 1 2 ᎏ = ᎏ 1 1 6 ᎏ –2 –3 = ᎏ – 1 2 3 ᎏ = ᎏ – 1 8 ᎏ = – ᎏ 1 8 ᎏ Rational Exponents Recall that rational numbers are all numbers that can be written as fractions ( ᎏ 2 3 ᎏ ), terminating decimals (.75), and repeating decimals (.666 . . . ). Keeping this in mind, it’s no surprise that numbers raised to rational exponents are just numbers raised to a fractional power. What is the value of 4 ᎏ 1 2 ᎏ ? 4 ᎏ 1 2 ᎏ can be rewritten as ͙4 ෆ , so it is equal to 2. Any time you see a number with a fractional exponent, the numerator of that exponent is the power you raise the number to, and the denominator is the root you take. Examples: 25 = ͙ 2 25 1 ෆ 8= ͙ 3 8 1 ෆ 16 = ͙ 2 16 1 ෆ Divisibility and Factors Like multiplication, division can be represented in a few different ways: 8 ÷ 3 3ͤ8 ෆ ᎏ 8 3 ᎏ In each of the above, 3 is the divisor and 8 is the dividend. Odd and Even Numbers An even number is a number that can be divided by the number 2:2,4,6,8,10,12,14, An odd number can- not be divided evenly by the number 2: 1, 3, 5, 7, 9, 11, 13, The even and odd numbers listed are also exam- ples of consecutive even numbers and consecutive odd numbers because they differ by two. Here are some helpful rules for how even and odd numbers behave when added or multiplied: even + even = even and even × even = even odd + odd = even and odd × odd = odd odd + even = odd and even × odd = even Dividing by Zero Dividing by zero is not possible. This is important to remember when solving for a variable in the denomi- nator of a fraction. Example: ᎏ a – 6 3 ᎏ In this problem, we know that a cannot be equal to 3, because that would yield a zero in the denominator. a – 3 = 0 a ≠ 3 ᎏ 1 2 ᎏ ᎏ 1 3 ᎏ ᎏ 1 2 ᎏ –THE SAT MATH SECTION– 113 5658 SAT2006[04](fin).qx 11/21/05 6:44 PM Page 113 Factors and Multiples Factors are numbers that can be divided into a larger number without a remainder. Example: 12 ÷ 3 = 4 The number 3 is, therefore, a factor of the number 12. Other factors of 12 are 1, 2, 4, 6, and 12. The common factor of two numbers are the fac- tors that both numbers have in common. Example: The factors of 24 = 1, 2, 3, 4, 6, 8, 12, and 24. The factors of 18 = 1, 2, 3, 6, 9, and 18. From the above, you can see that the common factors of 24 and 18 are 1, 2, 3, and 6. From this list, we can also determine that the greatest common factor of 24 and 18 is 6. Determining the greatest common fac- tor is useful for reducing fractions. Any number that can be obtained by multiplying a number x by a positive integer is called a multiple of x. Example: Some multiples of 5 are: 5, 10, 15, 20, 25, 30, 35, 40 . . . Some multiples of 7 are: 7, 14, 21, 28, 35, 42, 49, 56 . . . From the above, you can also determine that the least common multiple of the numbers 5 and 7 is 35. The least common multiple, or LCM, is used when performing various operations with fractions. Prime and Composite Numbers A positive integer that is greater than the number 1 is either prime or composite, but not both. ■ A prime number has only itself and the number 1 as factors. Examples: 2,3,5,7,11,13,17,19,23, ■ A composite number is a number that has more than two factors. Examples: 4,6,8,9,10,12,14,15,16, ■ The number 1 is neither prime nor composite. Prime Factorization The SAT will ask you to combine several skills at once. One example of this, called prime factorization, is a process of breaking down factors into prime numbers. Examples: 18 = 9 × 2 The number 9 can also be written as 3 × 3. So, the prime factoriza- tion of 18 is: 18 = 3 × 3 × 2 This can also be demonstrated with the factors 6 and 3: 18 = 6 × 3 Because we know that 6 is equal to 2 × 3, we can write: 18 = 2 × 3 × 3 According to the commutative law, we know that 3 × 3 × 2 = 2 × 3 × 3. Number Lines and Signed Numbers You have surely dealt with number lines in your career as a math student. The concept of the number line is simple: Less than is to the left and greater than is to the right . . . Sometimes, however, it is easy to get confused about the value of negative numbers. To keep things simple, remember this rule: If a > b, then –b > –a. Example: If 7 > 5, then –5 > –7. –7 –6 –5 –4 –3 –2 –1 0 1 2 3 4 5 6 7 Greater Than Less Than –THE SAT MATH SECTION– 114 5658 SAT2006[04](fin).qx 11/21/05 6:44 PM Page 114 [...]... All the numbers within a set are called the members of the set For example, the set of integers looks like this: { –3, –2 , –1, 0, 1, 2, 3, } The set of whole numbers looks like this: { 0, 1, 2, 3, } 116 5658 SAT2 006[04](fin).qx 11/21/05 6:44 PM Page 117 – THE SAT MATH SECTION – When you find the elements that two (or more) sets have in common, you are finding the intersection of the sets The. .. 120 To isolate the x variable, move the 4y to the other side Then divide both sides by the coefficient of x The last step is to simplify your answer This expression for x is written in terms of y 5658 SAT2 006[04](fin).qx 11/21/05 6:44 PM Page 121 – THE SAT MATH SECTION – Note that the sign of the term 8z changes twice because it was being subtracted twice Polynomials A polynomial is the sum or difference... multiply according to the FOIL order and then add the products Change all subtraction within the parentheses first: (8x + –7y + 9z) – (15x + 10y + –8z) Then change the subtraction sign outside of the parentheses to addition and the sign of each polynomial being subtracted: (8x + –7y + 9z) + (–15x + –10y + 8z) 121 5658 SAT2 006[04](fin).qx 11/21/05 6:44 PM Page 122 – THE SAT MATH SECTION – I SOLATING VARIABLES... Find the average of the numbers 3 and 5: ᎏ2ᎏ = 4 The answer is 4 The mode of a set of numbers is the number that occurs the greatest number of times If we were to combine the set of positive even numbers with the set of positive odd numbers, we would have the union of the sets: {1, 2, 3, 4, 5, } Example: For the number set 1, 2, 5, 3, 4, 2, 3, 6, 3, 7, the number 3 is the mode because it occurs the. .. Sometimes, there are x values that are outside of the domain, and these are the x values for which the function is not defined When f(x) = 3, the y value (use the y-axis) will equal 3 As shown below, there are five such points 126 5 4 3 2 1 –7 –6 –5 –4 –3 –2 –1 –1 –2 –3 y 1 2 3 4 5 6 7 x 5658 SAT2 006[04](fin).qx 11/21/05 6:44 PM Page 127 – THE SAT MATH SECTION – Geometr y Review To begin this section, ... of the sets The symbol for intersection is: ∩ For example, the intersection of the integers and the whole numbers is the set of the whole numbers itself This is because the elements (numbers) that they have in common are {0, 1, 2, 3, } Consider the set of positive even integers and the set of positive odd integers The positive even integers are: ■ {2, 4, 6, 8, } The positive odd integers are:... Example: Find the median of the number set: 1, 5, 3, 7, 2 First, arrange the set in ascending order: 1, 2, 3, 5, 7, and then, choose the middle value: 3 The answer is 3 If the set contains an even number of elements, simply average the two middle values Example: Find the median of the number set: 1, 5, 3, 7, 2, 8 First, arrange the set in ascending order: 1, 2, 3, 5, 7, 8, and then, choose the middle... sides C m∠a = m∠b Equilateral B 131 b a A 5658 SAT2 006[04](fin).qx 11/21/05 6:44 PM Page 132 – THE SAT MATH SECTION – ■ In equilateral triangles, all sides are equal and all angles are equal a2 + b2 = c2 12 + 22 = c2 1 + 4 = c2 5 = c2 ͙5 = c ෆ Equilateral 60º 5 Pythagorean Triples In a Pythagorean triple, the square of the largest number equals the sum of the squares of the other two numbers 5 60º 60º 5... you must find the least common denominator, or LCD For example, if given the denominators 8 and 12, 24 would be the LCD because 8 × 3 = 24 and 12 × 2 = 24 In other words, the LCD is the smallest number divisible by each of the denominators Once you know the LCD, convert each fraction to its new form by multiplying both the numerator and denominator by the necessary number to get the LCD, and then add or... substituted into the equation For example, below is the graph of y = x2 Zero-Product Rule The zero-product rule states that if the product of two or more numbers is 0, then at least one of the numbers is 0 5 4 3 2 1 –7 –6 –5 –4 –3 –2 –1 –1 –2 –3 y Example: (x + 5)(x – 3) = 0 123 1 2 3 4 5 6 7 x 5658 SAT2 006[04](fin).qx 11/21/05 6:44 PM Page 124 – THE SAT MATH SECTION – For every number you put into the equation . 25͙3 ෆ e. 25͙3 ෆ ᎏ 3 12.5͙3 ෆ ᎏ 3 30 o 12.5 h THE SAT MATH SECTION 105 5658 SAT2 006[04](fin).qx 11/21/05 6:44 PM Page 105 Grid-in Questions For the next 15 questions, solve the problem and enter your solution into the grid by marking the. positive integers, then the number of integers from A to B is (A – B) + 1. Therefore, the number of tickets is equal to (5,085 – 5,027) + 1 = 59. THE SAT MATH SECTION 108 5658 SAT2 006[04](fin).qx. example, in the expression 3 2 = 3 × 3 = 9, the number 9 is the square of the number 3. If we reverse the process, we can say that the number 3 is the square root of the number 9. The symbol for