沃邦年終總結|2019年度GMAT考試數學部分全面總結

沃邦國際教育 發佈 2020-01-31T15:58:05+00:00

例7The function f is defined for each positive three-digit integer n by f, where x, y, and z are the hundreds, tens, and units digits of n, r


根據官方指南,GMAT 數學中可能出現的考點可歸為四大類:算術、代數、幾何、應用題。具體涉及的概念如下:

算術:整數性質、分數、小數、實數、比值及比例、百分比、次方及次方根、描述性統計、集合、排列組合、離散機率;

代數:代數式化簡、方程、解一元一次方程、解二元一次方程組、因式分解、解二次方程、指數運算、不等式、絕對值、函數;

幾何:直線、相交線及角度、垂線、平行線、凸多邊形、三角形、四邊形、圓、長方體及圓柱體、坐標幾何;

應用題:速率問題、工作效率問題、混合物問題、利率問題、打折問題、利潤問題、集合問題、幾何問題、單位換算問題、圖表數據理解。

對於廣大中國考生而言,GMAT 數學通常不是一項特別高要求的挑戰,然而這並不意味著考試中所有題目都易如反掌:首先,GMAT 數學部分不允許參試者使用計算器,這一方面對手算的可靠度提出了要求,另一方面也迫使考生在某些原本可依賴計算器的題目中必須動腦筋巧算;其次,數論、集合容斥原理、排列組合、機率等幾個概念可稱得上是相對的難點,尤其對於數學基礎本不雄厚的文科生而言,更可能帶來不小困難;另外,GMAT 數學特有的題型——數據充分性解題思路比較特別,需要考生擁有十分清晰的邏輯思維。

下面就看一看上述幾個難點的例題:


1.數論


例1

If n=20!+17, then n is divisible by which of the following?

I. 15

II. 17

III. 19

A. None

B. I only

C. II only

D. I and II

E. II and III

答案為 C。

例2

When positive integer x is divided by positive integer y, the remainder is 9. If x/y=96.12, what is the value of y?

A. 96

B. 75

C. 48

D. 25

E. 12

答案為 B。

例3

If p is the product of the integers from 1 to 30, inclusive, what is the greatest integer k for which 3^k is a factor of p?

A. 10

B. 12

C. 14

D. 16

E. 18

答案為 C。

例4

If d=1/(2^3*5^7) is expressed as a terminating decimal, how many nonzero digits will d have?

A. One

B. Two

C. Three

D. Seven

E. Ten

答案為 B。

例5

If n is a positive integer, for which of the following values of k i 25*10^n+k*10^2n divisible by 9?

A. 9

B. 16

C. 23

D. 35

E. 47

答案為 E。

例6

For every even positive integer m, f(m) represents the product of all even integers from 2 to m, inclusive. For example, f(12)=2*4*6*8*10*12. What is the greatest prime factor of f(24)?

A. 23

B. 19

C. 17

D. 13

E. 11

答案為 E。

例7

The function f is defined for each positive three-digit integer n by f(n)=(2^x)(3^y)(5^z), where x, y, and z are the hundreds, tens, and units digits of n, respectively. If m and v are three-digit positive integers such that f(m)=9f(v), then m-v=

A. 8

B. 9

C. 18

D. 20

E. 80

答案為 D。

例8

If n is a positive integer and n^2 is divisible by 72, then the largest positive integer that must divide n is

A. 6

B. 12

C. 24

D. 36

E. 48

答案為 B。

例9

If x and y are positive integers, what is the remainder when 10^x+y is divided by 3?

(1) x=5

(2) y=2

答案為 B。

例10

If a and b are positive integers, what is the value of the product ab?

(1) The least common multiple of a and b is 48.

(2) The greatest common factor of a and b is 4.

答案為 C。

例11

If a, b, and c are consecutive integers and 0<a<b<c, is the product abc a multiple of 8?

(1) The product ac is even.

(2) The product bc is a multiple of 4.

答案為 A。

例12

If x and y are positive integers, is xy even?

(1) x^2+y^2-1 is divisible by 4.

(2) x+y is odd.

答案為 D。

例13

If x, y, and z are three-digit positive integers and if x=y+z, is the hundreds digit of x equal to the sum of the hundreds digits of y and z?

(1) The tens digit of x is equal to the sum of the tens digits of y and z.

(2) The units digit of x is equal to the sum of the units digits of y and z.

答案為 A。


2.集合的容斥原理


例14

Of the 150 houses in a certain development, 60 percent have air-conditioning , 50 percent have a sunporch, and 30 percent have a swimming pool. If 5 of the houses have all three of these amenities and 5 have none of them, how many of the houses have exactly two of these amenities?

A. 10

B. 45

C. 50

D. 55

E. 65

答案為 D。

例15

Last year in a group of 30 businesses, 21 reported a net profit and 15 had investments in foreign markets. How many of the businesses did not report a net profit nor invest in foreign markets last year?

(1) Last year 12 of the 30 businesses reported a net profit and had investments in foreign markets.

(2) Last year 24 of the 30 businesses reported a net profit or invested in foreign markets, or both.

答案為 D。

例16

Of a group of 50 households, how many have at least one cat or at least one dog, but not both?

(1) The number of households that have at least one cat and at least one dog is 4.

(2) The number of households that have no cats and no dogs is 14.

答案為 C。


3.排列組合


例17

Clarissa will create her summer reading list by randomly choosing 4 books from the 10 book approved for summer reading. She will list the books in the order in which they are chosen. How many different lists are possible?

A. 6

B. 40

C. 210

D. 5040

E. 151200

答案為 D。

例18

A three-digit code for certain locks uses the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 according to the following constraints. The first digit cannot be 0 or 1, the second digit must be 0 or 1, and the second and third digits cannot both be 0 in the same code. How many different codes are possible?

A. 144

B. 152

C. 160

D. 168

E. 176

答案為 B。

例19

Team A and Team B are competing against each other in a game of tug-of-war. Team A, consisting of 3 males and 3 females, decides to line up male, female, male, female, male, female. The lineup that Team A chooses will be one of how many different possible lineups?

A. 9

B. 12

C. 15

D. 36

E. 720

答案為 D。

例20

The letters D, G, I, I and T can be used to form 5-letter strings such as DIGIT or DGIIT. Using these letters, how many 5-letter strings can be formed in which the two occurrences of the letter I are separated by at least one other letter?

A. 12

B. 18

C. 24

D. 36

E. 48

答案為D。

例21

A certain university will select 1 of 7 candidates eligible to fill a position in the mathematics department and 2 of 10 candidates eligible to fill 2 identical positions in the computer science department. If none of the candidates is eligible for a position in both departments, how many different sets of 3 candidates are there to fill the 3 positions?

A. 42

B. 70

C. 140

D. 165

E. 315

答案為E。

例22

How many subsets of the set {w, x, y, z} contain w?

A. Four

B. Five

C. Seven

D. Eight

E. Sixteen

答案為D。

例23

There are 5 cars to the displayed in 5 parking spaces, with all the cars facing the same direction. Of the 5 cars, 3 are red, 1 is blue, and 1 is yellow. If the cars are identical except for color, how many different display arrangements of the 5 cars are possible?

A. 20

B. 25

C. 40

D. 60

E. 125

答案為A。

例24

There are 10 books on a shelf, of which 4 are paperbacks and 6 are hardbacks. How many possible selections of the 5 books from the shelf contain at least one paperback and at least one hardback?

A. 75

B. 120

C. 210

D. 246

E. 252

答案為D。


4.機率

例25

In a box of 12 pens, a total of 3 are defective. If a customer buys 2 pens selected at random from the box, what is the probability that neither pen will be defective?

A. 1/6

B. 2/9

C. 6/11

D. 9/16

E. 3/4

答案為 C。

例26

The probability that event M will not occur is 0.8 and the probability that event R will not occur is 0.6. If events M and R cannot both occur, which of the following is the probability that either event M or event R will occur?

A. 1/5

B. 2/5

C. 3/5

D. 4/5

E. 12/25

答案為 C。

例27

A couple decides to have 4 children. If they succeed in having 4 children and each child is equally likely to be a boy or a girl, what is the probability that they will have exactly 2 girls and 2 boys?

A. 3/8

B. 1/4

C. 3/16

D. 1/8

E. 1/16

答案為 A。

例28

Jill has applied for a job with each of the two different companies. What is the probability that she will get the job offer from both companies?

(1) The probability that she will get a job offer from neither company is 0.3.

(2) The probability that she will get a job offer from exactly one of the two companies is 0.5.

答案為 C。


5.描述性統計


例29

For each student in a certain class, a teacher adjusted the student’s test score using the formula y=0.8x+20, where x is the student’s original test score and y is the student’s adjusted test score. If the standard deviation of the original test scores of the students in the class was 20, what was the standard deviation of the adjusted test scores of the students in the class?

A. 12

B. 16

C. 28

D. 36

E. 40

答案為 B。

例30

A certain characteristic in a large population has a distribution that is symmetric about the mean m. If 68 percent of the distribution lies within one standard deviation d of the mean, what percent of the distribution is less than m+d?

A. 16%

B. 32%

C. 48%

D. 84%

E. 92%

答案為 D。


例31

A scientist recorded the number of eggs in each of 10 birds』 nests. What was the standard deviation of the numbers of eggs in the 10 nests?

(1) The average (arithmetic mean) number of eggs for the 10 nests was 4.

(2) Each of the 10 nests contained the same number of eggs.

答案為 B。

例32

A certain list consists of 3 different numbers. Does the median of the 3 numbers equal the mean of the 3 numbers?

(1) The range of the 3 numbers is equal to twice the difference between the greatest numbers and the median.

(2) The sum of the 3 numbers is equal to 3 times one of the numbers.

答案為 D。


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