GMAT考试PREP-MATH-PS2完整详解版-V1.0(4)

(B) $16.66 (C) $20.00 (D) $26.66 (E) $40.00

------------------------------------------------------------------------------------------------------------------------------------ 【答案】C 【思路】

按照提議列出方程式 : M = 3N - 10

?50 = 3N -10 可得N=20

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60. 6711-!-item-!-187;#058&004926 The value of [?] is

(A) between -9 and -10 (B) between -8 and -9 (C) between -4 and -5 (D) between -3 and -4 (E) undefined

61. 6814-!-item-!-187;#058&004969 [?]

A computer chip manufacturer expects the ratio of the number of defective chips to the total number of chips in all future shipments to equal the corresponding ratio for shipments S1, S2, S3, and S4 combined, as shown in the table above. What is the expected number of defective chips in a shipment of 60,000 chips?

(A) 14 (B) 20 (C) 22 (D) 24 (E) 25

62. 7185-!-item-!-187;#058&005078

In a certain furniture store, each week Nancy earns a salary of $240 plus 5 percent of the amount of her total sales that exceeds $800 for the week. If Nancy earned a total of $450 one week, what were her total sales that week?

(A) $2,200 (B) $3,450 (C) $4,200 (D) $4,250 (E) $5,000

------------------------------------------------------------------------------------------------------------------------------- 【答案】E

【思路】設total sales 為X元, 則 240+(x-800) ? 0.05=450

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63. 7231-!-item-!-187;#058&005082

The sum of the first 50 positive even integers is 2,550. What is the sum of the even integers from 102 to 200, inclusive?

(A) 5,100 (B) 7,550 (C) 10,100 (D) 15,500 (E) 20,100

------------------------------------------------------------------------------------------------------------------------------ 【答案】B

【思路】2+4+6+8+10………100=2550,

102+104+106+108+110……200=(100+2)+(100+4)+(100+6)+(100+8)…….+(100+200) =50?100+(2+4+6+8+……….100) =5000+2550=7550

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64. 7285-!-item-!-187;#058&005104 [?]

A certain bank uses the formula above to approximate the annual percentage rate R of a monthly installment loan. Which of the following is an equivalent form of the formula?

(A) (B) (C) (D) (E)

65. 7385-!-item-!-187;#058&005343

A salesperson received a commission of 3 percent of the sale price for each of the first 100 machines that she sold and 4 percent of the sale price for each machine that she sold after the first 100. If the sale price of each machine was $10,000 and the salesperson received a $36,000 commission, how many machines did she sell?

(A) 90 (B) 103 (C) 105 (D) 115 (E) 120

------------------------------------------------------------------------------------------------------------------------------ 【答案】D

【思路】前100台commission-> 10000?100?0.03=30000 則(10000x) ?0.04=6000 x=15+100=115

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66. 7431-!-item-!-187;#058&005458

From a group of 21 astronauts that includes 12 people with previous experience in space flight, a 3-person crew is to be selected so that exactly 1 person in the crew has previous experience in space flight. How many different crews of this type are possible?

(A) 432 (B) 594 (C) 864 (D) 1,330 (E) 7,980

------------------------------------------------------------------------------------------------------------------------------ 【答案】A

【思路】12-previous experience, 9-previous experience,則2個沒經驗和1個有經驗的組合?

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67. 7481-!-item-!-187;#058&005467

S represents the sum of the weights of n fish in pounds. Which of the following represents the average (arithmetic mean) of the n weights in ounces? (1 pound = 16 ounces)

C121?C2=432

9(A) 16nS (B) (C) (D) (E)

68. 7638-!-item-!-187;#058&005506

In a certain bathtub, both the cold-water and the hot-water fixtures leak. The cold-water leak alone would fill an empty bucket in c hours, and the hot-water leak alone would fill the same bucket in h hours, where c < h. If both fixtures began to leak at the same time into the empty bucket at their respective constant rates and consequently it took t hours to fill the bucket, which of the following must be true? [?]

(A) I only (B) II only (C) III only (D) I and II (E) I and III

69. 8008-!-item-!-187;#058&005955

If (2^x)(3^y) = 288, where x and y are positive integers, then [2^(x - 1)][3^(y - 2)] =

(A) 16 (B) 24 (C) 48 (D) 96 (E) 144

------------------------------------------------------------------------------------------------------------------------------- 【答案】A 【思路】2405?32=288? x=5,y=2

則2?3=16

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70. 8217-!-item-!-187;#058&006107

If 3 - 3 = 162, then x(x - 1) =

(A) 12 (B) 16 (C) 20 (D) 30 (E) 81

------------------------------------------------------------------------------------------------------------------------------- 【答案】C

x(x?1)3(x?1) = 162, 12xxx4?1

則3(1-)=3?=3?2?3=2?3

33則X-1=4, X=5? 5?4=20

【思路】3 -

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71. 8372-!-item-!-187;#058&006254

For which of the following values of x is [?] NOT defined as a real number?

(A) 1 (B) 2 (C) 3

x(D) 4 (E) 5

72. 8421-!-item-!-187;#058&006278 [?]

(A) 1 (B) (C) (D) 18 (E) 20

73. 8467-!-item-!-187;#058&006379

The maximum temperatures, in degrees Fahrenheit, recorded in a city on 5 consecutive days were x + 3, 95, 87, x + 7, and x. If the average (arithmetic mean) of these temperatures was 90 degrees Fahrenheit, what is the value of x ?

(A) 85 (B) 86 (C) 87 (D) 88 (E) 89 --------------------------------------------------------------------------------------------------------------- 【答案】B 【思路】已知平均值，求未知數x : (x?3)?95?87?(x?7)?x?90=> 3x=258, x=86 5--------------------------------------------------------------------------------------------------------------- 74. 8516-!-item-!-187;#058&006446

There are 15 slate rocks, 20 pumice rocks, and 10 granite rocks randomly distributed in a certain field. If 2 rocks are to be chosen at random and without replacement, what is the probability that both rocks will be slate rocks?

(A) (B) (C) (D) (E)

75. 8673-!-item-!-187;#058&006582

The y-intercept of a line [?] is 4. If the slope of [?] is negative, which of the following could be the x-intercept of [?] ?

(A) I only (B) II only (C) III only (D) I and II (E) I and III

76. 8721-!-item-!-187;#058&006602

A hiker walking at a constant rate of 4 miles per hour is passed by a cyclist traveling in the same direction along the same path at a constant rate of 20 miles per hour. The cyclist stops to wait for the hiker 5 minutes after passing her, while the hiker continues to walk at her constant rate. How many minutes must the cyclist wait until the hiker catches up?

(A) (B) 15 (C) 20 (D) 25 (E)

77. 8876-!-item-!-187;#058&006751

A contest will consist of n questions, each of which is to be answered either \answers all n questions correctly will be a winner. What is the least value of n for which the probability is less than [?] that a person who randomly guesses the answer to each question will be a winner?

(A) 5 (B) 10 (C) 50 (D) 100 (E) 1,000

78. 9309-!-item-!-187;#058&006922 If , then x =

(A) c2 + (B) c6 + (C) c9 + (D) c12 + (E) c18 +

79. 9358-!-item-!-187;#058&006924 If ab is not 0, then a^(-1) + b^(-1) =

(A) a + (B) -(a + b) (C) (D) (E)

80. 9407-!-item-!-187;#058&006938

If 0 < x < 1, which of the following inequalities must be true? [?]

(A) None (B) I only (C) II only

(D) I and II only (E) I, II, and III

81. 9454-!-item-!-187;#058&006950 If [?], what is the value of n ?

(A) -2 (B) -1 (C) 0 (D) 1 (E) 2

82. 9500-!-item-!-187;#058&006955

If (2^x)(2^y) = 8 and (9^x)(3^y) = 81, then (x, y) =

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