GRE Math 강좌 Set 3

GRE Math 강좌 Set 3

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Category 3 Averages

1. What is the average (arithmetic mean) of the numbers 15, 16, 17, 17, 18, and 19?

(A) 14.2

(B) 16.5

(C) 17

(D) 17.5

(E) 18

2. If n red pencils cost 10 cents each and m blue pencils cost 9 cents each, what is the

average (arithmetic mean) cost, in cents, per pencil?

(A) 2

)(19 mn +

(B) 19

910 mn +

(C) mn

mn

++ 910

(D) 2

mn +

(E) mn +

19

3. If the average (arithmetic mean) of ,,ba and c is 40, what is the average (arithmetic

mean) of )103(),103( ++ ba , and )103( +c ?

(A) 50

(B) 70

(C) 130

(D) 150

(E) It cannot be determined from the information given.



4. The cost of item A is 2

y each and the cost of item B is

3

t each. What is the average

(arithmetic mean) cost per unit of a collection consisting of x units of A and k units of

B ?

(A) 12

23 ty +

(B) 12

)23()( tykx +++

(C) kx

ktxy

++ 23

(D) 6

23 ktxy +

(E) )(6

23

kx

ktxy

++

5. If each of 4 subsidiaries of Corporation R has been granted a line of credit of $700,000 and

each of the other 3 subsidiaries of Corporation R has been granted a line of credit of $112,000, what is the average (arithmetic mean) line of credit granted to a subsidiary of

Corporation R ? (A) $1,568,000

(B) $448,000

(C) $406,000

(D) $313,600

(E) $116,000

6. What is the average (arithmetic mean) of 8 numbers if the average of 5 of the numbers is 24

and the sum of the remaining 3 numbers is 40?

(A) 8

(B) 20

(C) 29

(D) 30

(E) 37.5



7. A manager’s annual salary is $8,400 greater than the annual salary of each of two assistant

managers, who earn x dollars each per year. The average (arithmetic mean) of the 3

annual salaries, in dollars, is

(A) 800,2+x

(B) 200,4+x

(C) 800,22 +x

(D) 3

400,82 +x

(E) 2

400,83 +x

8. If the average (arithmetic mean) of the four numbers K , 32 +K , 53 −K , and 15 +K is

63, what is the value of K ?

(A) 11

(B) 4

315

(C) 22

(D) 23

(E) 10

325

9. The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15

(B) 25

(C) 35

(D) 45

(E) 55



10. A total of $2,000 was spent for a 30-day vacation. If transportation expenses were $230,

lodging was $750, and exactly $20 was spent per day for meals and tips, what was the average

(arithmetic mean) amount per day that was spent on other expenses?

(A) $66

(B) $42

(C) $33 (D) $20

(E) $14

11. In a certain company, the total monthly payroll for the 12 production workers is $18,000 and

the total monthly payroll for the 36 office workers is $63,000. By how much does the average

(arithmetic mean) monthly salary of an office worker exceed that of a production worker in

this company?

(A) $62.50

(B) $187.50

(C) $250.00

(D) $375.00

(E) $500.00

12. On a certain test, 3 students each had a score of 90, 9 students each had a score of 80, 4

students each had a score of 70, and 4 students each had a score of 60. What was the average

(arithmetic mean) score for the 20 students?

(A) 70.5 (B) 75.0

(C) 75.5

(D) 80.0

(E) 80.5



<High Level Questions>

13. On 3 sales John has received commissions of $240, $80, and $110, and he has 1 additional sale

pending. If John is to receive an average (arithmetic mean) commission of exactly $150 on

the 4 sales, then the 4th commission must be.

(A) $164

(B) $170

(C) $175

(D) $182

(E) $185

14. The 10 households on a certain street have household incomes that range from $34,000 to

$150,000 and an average (arithmetic mean) household income of $60,000. If the household

with the highest income and the one with the lowest income are excluded, what is the average

household income for the remaining 8 households?

(A) $41,600

(B) $47,000

(C) $52,000

(D) $61,000

(E) $75,000

15. The graph above shows the distribution of the 100 scores in a certain competition. What is

the median score for the competition?

(A) 7.5

(B) 7.75

(C) 8.0

(D) 8.25

(E) 8.5



16. A certain elevator has a safe weight limit of 2,000 pounds. What is the greatest possible

number of people who can safely ride on the elevator at one time with the average (arithmetic

mean) weight of half the riders being 180 pounds and the average weight of the others being

215 pounds?

(A) 7

(B) 8 (C) 9

(D) 10

(E) 11

17. For the month of April, the average (arithmetic mean) of the daily high temperatures

recorded at a certain weather station was x degrees. If the average for the first 13 days of

the month was )10( −x degrees, what was the average, in degrees, for the remaining 17 days

of the month?

(A) 10+x

(B) 13017 +x

(C) x

x 17130 +

(D) 17

1017 +x

(E) 17

13017 +x

18. A statistician calculated the average (arithmetic mean) for 20 measurements to be 50. On

rechecking the calculations, the statistician found that a measurement of “78” had been treated

as “18” and a measurement of “40” had been treated as “50”. If no other errors were made,

what is the correct average for the 20 measurements?

(A) 47.5

(B) 50.0

(C) 51.0

(D) 52.5

(E) 53.5



19. If k is an integer and 2515 << k , which of the following could be the average (arithmetic

mean) of 12, 14, 17, 23, and k ?

(A) 13.2

(B) 15.6

(C) 16.8

(D) 18.2

(E) 19.5

20. In performing a sequence of experiments, a scientist made 20 measurements. The average

(arithmetic mean) of these measurements was 34. For security reasons the scientist coded the

data by multiplying each of the measurements by 10 and then adding 40 to each product.

What is the average of the coded measurements?

(A) 1,140

(B) 380

(C) 342 (D) 57

(E) 19

21. The average (arithmetic mean) of n numbers is equal to 3

1 the sum of the n numbers.

If 2

1 the sum of the numbers is 15, what is the average of the n numbers?

(A) 3

(B) 5

(C) 10 (D) 30

(E) 45



22. The average (arithmetic mean) of ten numbers on a list is m . If the numbers 10 and 24 are

added to the list, the average (arithmetic mean) of these twelve numbers on the list is also m .

What is the value of m ?

(A) 3

111

(B) 14

(C) 17 (D) 20


23. The average (arithmetic mean) price of the 5 houses on a certain street is $60,000. If the

price of the least expensive house is $55,000 which of the following could NOT be the price of

the most expensive house?

(A) $82,000

(B) $78,000

(C) $72,000

(D) $65,000

(E) $62,500

24. If the average (arithmetic mean) of x and y is 60 and the average (arithmetic mean) of y

and z is 80, what is the value of xz − ?

(A) 70

(B) 40

(C) 20

(D) 10




Mon Tue Wed Thu Fri

2

12+

4

11−

8

1−

0 8

31+

25. The table above shows the net change, in dollars, in the price of a share of a certain stock each

day last week. What was the average (arithmetic mean) daily net change, in dollars, for the 5-

day week?

(A) 2

1− (B)

4

1+ (C)

2

1+ (D)

4

5+ (E)

2

5+

26. If the average (arithmetic mean) of 5 positive temperatures is x degrees Fahrenheit, then the

sum of the 3 greatest of these temperatures, in degree Fahrenheit, could be

(A) x6

(B) x4

(C) 3

5x

(D) 2

3x

(E) 5

3x

Score Number of

Students

83 5

70 6

92 3

5

64 1

27. The incomplete table above shows a distribution of scores for a class of 20 students. If the

average (arithmetic mean) score for the class is 78, what score is missing from the table?

(A) 73

(B) 75

(C) 77

(D) 79

(E) 81



28. If x is the average (arithmetic mean) of 5 consecutive even integers, which of the following

must be true?

I. x is an even integer.

II. x is a nonzero integer.

III. x is a multiple of 5.

(A) I only

(B) III only

(C) I and II only

(D) I and III only

(E) I, II, and III

29. The average (arithmetic mean) of 4 positive integers is 50. If the average of 2 of these

integers i s 45, what is the greatest possible value that one of the other 2 integers can have?

(A) 55

(B) 65

(C) 100 (D) 109

(E) 115

30. The trade name for a product has 6 letters , and the length of the package for the product is

l centimeters. The trade name of the product is printed lengthwise on one side of the

package with a margin of m centimeters on each end of the side. If the space between each

letter is considered negligible, what is the average (arithmetic mean) width, in centimeters, of each letter in the trade name?

(A) m2−l

(B) m−l

(C) 8÷l

(D) 6)( ÷− ml

(E) 6)2( ÷− ml



수학 해설 Category 3 Average

1. What is the average (arithmetic mean) of the numbers 15, 16, 17, 17, 18, and 19? (A) 14.2

(B) 16.5

(C) 17

(D) 17.5

(E) 18

176

191817171615=

+++++ ,

: 정답은 (C) :

2. If n red pencils cost 10 cents each and m blue pencils cost 9 cents each, what is the

average (arithmetic mean) cost, in cents, per pencil?

(A) 2

)(19 mn +

(B) 19

910 mn +

(C) mn

mn

++ 910

(D) 2

mn +

(E) mn +

19

N1(개수)을 가진 그룹의 평균은 A1, N2(개수)의 평균은 A2 일 때

Combined Average(N1 과 N2 의 혼합된 평균) = 21

)22()11(

NN

ANAN

+×+×

n 의 평균은 10cents, m 의 평균은 9 cents 이니까, 위의 공식에 대입하면 정답을 구할 수 있죠.

: 정답은 (C) :

Point! 혼합평균 공식을 이용하는 문제가 자주 출제됩니다. N1은 한 집단의 수를 나타내고, N2도

다른 집단의 수를 나타낸다. 두 집단의 평균을 합쳐서 새로운 평균(Combined Average)을 구하는

문제이므로 위의 공식에 정확히 대입하면 그리 어려운 문제는 아닙니다.



3. If the average (arithmetic mean) of ,,ba and c is 40, what is the average (arithmetic

mean) of )103(),103( ++ ba , and )103( +c ?

(A) 50

(B) 70

(C) 130

(D) 150 (E) It cannot be determined from the information given.

403

=++ cba , then

3

)103()103()103( +++++ cba =?

120=++ cba 을 위의 식에 대입하면 정답을 구할 수 있죠.

: 정답은 (C) :

4. The cost of item A is 2

y each and the cost of item B is

3

t each. What is the average

(arithmetic mean) cost per unit of a collection consisting of x units of A and k units of

B ?

(A) 12

23 ty +

(B) 12

)23()( tykx +++

(C) kx

ktxy

++ 23

(D) 6

23 ktxy +

(E) )(6

23

kx

ktxy

++

N1( x )의 그룹의 평균은 A1(2

y), N2( k )의 평균은 A2(

3

t)일 때

Combined Average(N1과 N2 의 혼합된 평균)

= 21

)22()11(

NN

ANAN

+×+×

=kx

tk

yx

+

×+× )3

()2

( 이 식을 정리하면

: 정답은 (E) :

5. If each of 4 subsidiaries of Corporation R has been granted a line of credit of $700,000 and

each of the other 3 subsidiaries of Corporation R has been granted a line of credit of $112,000, what is the average (arithmetic mean) line of credit granted to a subsidiary of

Corporation R ? (A) $1,568,000

(B) $448,000

(C) $406,000

(D) $313,600

(E) $116,000



Combined Average를 묻는 문제네요!!

21)22()11(

NNANAN

+×+×

= 000,448$7

)000,112$3()000,700$4(=

×+×

: 정답은 ( B ) :

6. What is the average (arithmetic mean) of 8 numbers if the average of 5 of the numbers is 24

and the sum of the remaining 3 numbers is 40? (A) 8

(B) 20

(C) 29

(D) 30

(E) 37.5

Combined Average 공식을 사용하면 되죠! 8개의 숫자 중에서 5개의 평균은 24이고, 나머지 3개의

합은 40이라 했으니까 나머지 3개의 숫자의 평균은 40/3 이네요. 이것을 가지고 공식에 대입하면 :

)(208

)3

403()245(

Average=×+×

,

: 정답은 (B) :

7. A manager’s annual salary is $8,400 greater than the annual salary of each of two assistant

managers, who earn x dollars each per year. The average (arithmetic mean) of the 3

annual salaries, in dollars, is

(A) 800,2+x

(B) 200,4+x

(C) 800,22 +x

(D) 3

400,82 +x

(E) 2

400,83 +x

A manager’s annual salary = $ x (salary of each of two assistant managers) + $8,400

Average= 800,2$3

)400,8$(+=

+++x

xxx ,

: 정답은 (A) :



8. If the average (arithmetic mean) of the four numbers K , 32 +K , 53 −K , and 15 +K is

63, what is the value of K ?

(A) 11

(B) 4

315

(C) 22

(D) 23

(E) 10

325

63

4

)15()53()32(=

++−+++ KKKK

왼쪽의 식을 풀면 K=23,

: 정답은 (D) :

9. The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15 (B) 25 (C) 35 (D) 45 (E) 55

3

4020530

3

503010 x+++==

++ 이 식을 정리하면 X 값을 구할 수 있습니다.

: 정답은 (A) :

10. A total of $2,000 was spent for a 30-day vacation. If transportation expenses were $230,

lodging was $750, and exactly $20 was spent per day for meals and tips, what was the average

(arithmetic mean) amount per day that was spent on other expenses?

(A) $66

(B) $42

(C) $33

(D) $20

(E) $14

전체경비($2,000) − ($230+$750+($20×30days) = $420(other expenses)

$420 ÷30 = $14,

: 정답은 (E) :

Tip :exactly $20 was spent per day for meals and tips 의미는 매일 $20을 식사비와 팁으로

섰다는 것이므로 여기에 30 days을 곱해야지 전체 식사비와 팁이 나옵니다.



11. In a certain company, the total monthly payroll for the 12 production workers is $18,000 and

the total monthly payroll for the 36 office workers is $63,000. By how much does the average

(arithmetic mean) monthly sal ary of an office worker exceed that of a production worker in

this company?

(A) $62.50 (B) $187.50

(C) $250.00

(D) $375.00

(E) $500.00

12 production workers 의 평균 = 500,1$12

000,18$=

36 office workers 의 평균 = 750,1$36

000,63$=

따라서 평균의 차이는 $1,750 -- $1,500 = $250,

: 정답은 (C) :

12. On a certain test, 3 students each had a score of 90, 9 students each had a score of 80, 4

students each had a score of 70, and 4 students each had a score of 60. What was the average (arithmetic mean) score for the 20 students?

(A) 70.5

(B) 75.0

(C) 75.5

(D) 80.0

(E) 80.5

Combined average 을 묻는 문제입니다!

Combined Average = 5.754493

)604()704()809()903(=

+++×+×+×+× ,

: 정답은 (C) :

<High Level Questions 수학해설>

13. On 3 sales John has received commissions of $240, $80, and $110, and he has 1 additional sale

pending. If John is to receive an average (arithmetic mean) commission of exactly $150 on

the 4 sales, then the 4th commission must be. (A) $164 (B) $170 (C) $175 (D) $182 (E) $185

150$4

11080240 =+++ x , 이 식을 정리하면 x = $170

: 정답은 (B) :



14. The 10 households on a certain street have household incomes that range from $34,000 to

$150,000 and an average (arithmetic mean) household income of $60,000. If the household

with the highest income and the one with the lowest income are excluded, what is the average

household income for the remaining 8 households?

(A) $41,600 (B) $47,000 (C) $52,000 (D) $61,000 (E) $75,000

000,60$10

000,150$)8(000,34$=

++ households,

이 식에서 가장 낮은 값과 높은 값을 정리하면 8 households income = $416,000,

이 값을 다시 8로 나누면 $52,000. 정답!

: 정답은 (C) :

15. The graph above shows the distribution of the 100 scores in a certain competition. What is

the median score for the competition? (A) 7.5 (B) 7.75 (C) 8.0 (D) 8.25 (E) 8.5

median(중앙값)을 구할 때는 변량( nx)으로, 여기서는 scores, 구하는 것이 아니라

frequency(빈도) 값의 중앙값을 구하는 것입니다. 여기서 frequency는 100이고 median은 50번

째 값이므로 이 값을 찾으면 됩니다. 가장 큰 score인 10.0의 frequency부터 대략 계산하면

2(10.0) + 4(9.5) + 5(9.0) + 25(8.5) ≈ 36이고 score 8.0의 frequency는 20이므로 50번째 frequency는

반드시 score 8.0에 존재한다는 것을 알 수 있습니다.

: 정답은 (C) :

16. A certain elevator has a safe weight limit of 2,000 pounds. What is the greatest possible

number of people who can safely ride on the elevator at one time with the average (arithmetic

mean) weight of half the riders being 180 pounds and the average weight of the others being

215 pounds?

(A) 7 (B) 8 (C ) 9 (D) 10 (E) 11

엘리베이터에 탈 수 있는 전체 사람수를 R이라 하면

poundsR

1802

+ poundsR

2152

≈ 2,000 pounds,

위의 식에서 R의 최대값은 10이 되겠죠.



: 정답은 (D) :

17. For the month of April, the average (arithmetic mean) of the daily high temperatures

recorded at a certain weather station was x degrees. If the average for the first 13 days of

the month was )10( −x degrees, what was the average, in degrees, for the remaining 17 days

of the month?

(A) 10+x (B) 13017 +x (C)x

x 17130 + (D)

17

1017 +x (E)

17

13017 +x

여기서 17일의 평균 온도를 y 라 가정하면 아래의 식을 구할 수 있습니다:

xyx

=+−

30

17)10(13, 이 식을 in terms of x 에 의해 y 를 구하면 답을 구할 수 있죠.

: 정답은 (E) :

18. A statistician calculated the average (arithmetic mean) for 20 measurements to be 50. On

rechecking the calculations, the statistician found that a measurement of “78” had been treated

as “18” and a measurement of “40” had been treated as “50”. If no other errors were made,

what is the correct average for the 20 measurements?

(A) 47.5 (B) 50.0 (C) 51.0 (D) 52.5 (E) 53.5

통계학자는 20개의 측정치에 대한 평균은 50이라고 계산했습니다. 검산 중에 측정치78을

18로 40을 50으로 잘못 계산했다고 합니다.올바른 평균값을 물어 보고 있습니다.

측정치 78을 18로 계산했으면 +60만큼의 차이가 40을 50으로 계산했으면 –10만큼의 오류가

발생했습니다. 따라서 두 값의 합인 50을 20으로 나누어 그 값 2.5을 기존에 구했던 평균

값 50에 더하여 주면 52.5가 됩니다.

: 정답은 (D)입니다. :

19. If k is an integer and 2515 << k , which of the following could be the average (arithmetic

mean) of 12, 14, 17, 23, and k ?

(A) 13.2

(B) 15.6

(C) 16.8

(D) 18.2

(E) 19.5

12, 14, 17, 23의 합은 66입니다. K값의 범위만이 주어져 있으므로 평균값을 구하기 위한 5개

정수 합의 범위는 81(=66+15) < sum < 91(=66+25)인 것을 알 수 있습니다. 81와 91을 5로

나누어 평균을 구해보면 16.2 < average < 18.2, 보기 중에서 이 범위에 해당하는 평균의 값은

16.8뿐입니다.

ÿ 정답은 (C)입니다.



20. In performing a sequence of experiments, a scientist made 20 measurements. The average

(arithmetic mean) of these measurements was 34. For security reasons the scientist coded the

data by multiplying each of the measurements by 10 and then adding 40 to each product.

What is the average of the coded measurements?

(A) 1,140 (B) 380 (C) 342 (D) 57 (E) 19

20회 측정의 평균값이 34, 그러면 총 합은 )(3420

averagesum

= 20×34 = 680입니다.

여기서 각 measurement에 10을 곱했다면 그 값은 680에 10을 곱한 값 6800과 같습니다.

이번에는 각 measurement에 40씩 더했다면 그 값은 40×20 = 800이 되고 위의 값 6800과

800을 더한 후 20으로 나누어주면 7600 ÷ 20 = 380. 이 값이 우리가 찾는 값이네요.

: 정답은 (B) :

21. The average (arithmetic mean) of n numbers is equal to 3

1 the sum of the n numbers.

If 2

1 the sum of the numbers is 15, what is the average of the n numbers?

(A) 3 (B) 5 (C) 10 (D) 30 (E) 45

Average = sumn

sum

3

1= , 여기서 n 은 3임을 알 수 있죠. 다시

2

1 the sum of the numbers is

15에서 the sum of number = 30, 여기서 n 의 평균은 103

30=

: 정답은 (C) :

22. The average (arithmetic mean) of ten numbers on a list is m . If the numbers 10 and 24 are

added to the list, the average (arithmetic mean) of these twelve numbers on the list is also m .

What is the value of m ?

(A) 3

111 (B) 14 (C) 17 (D) 20


12

34

10

+==

summ

sum, 왼쪽 식에서 sum을 m값으로 표현하면

1sum = 10m, 2sum = 12m – 34 ⇒ 10m = 12m − 34 이 식을 정리하면 m = 17

: 정답은 (C) :



23. The average (arithmetic mean) price of the 5 houses on a certain street is $60,000. If the

price of the least expensive house is $55,000 which of the following could NOT be the price of

the most expensive house?

(A) $82,000 (B) $78,000 (C) $72,000 (D) $65,000 (E) $62,500

000,60$5

5=

houses, 다섯 집 가격의 sum은 $300,00입니다. 여기서 가장 싼 집의 가격이

$55,000이라 했죠. 나머지 네 집 중 가장 비싼 집을 제외한 세 집의 가격을 최저 가격인

$55,000이라 가정하면 네 집의 가격은 4×$55,000 = $220,000. 다시 $300,00에서 $220,000을

빼면 가장 비싼 집의 최대값 $80,000을 구할 수 있습니다. 따라서 마지막 집은 $80,000을

절대로 넘어서는 안됩니다.

: 정답은 (A) :

24. If the average (arithmetic mean) of x and y is 60 and the average (arithmetic mean) of y

and z is 80, what is the value of xz − ?

(A) 70 (B) 40 (C) 20 (D) 10


쉽지만 한 번 풀어보는 것이 좋은 문제네요.

802

,602

=+

=+ zyyx

⇒ 160,120 =+=+ zyyx

따라서 xz − = 40

: 정답은 (B) :

Mon Tue Wed Thu Fri

2

12+

4

11−

8

1−

0 8

31+

25. The table above shows the net change, in dollars, in the price of a share of a certain stock each

day last week. What was the average (arithmetic mean) daily net change, in dollars, for the 5-

day week?

(A) 2

1− (B)

4

1+ (C)

2

1+ (D)

4

5+ (E)

2

5+

아주 쉬운 문제인데 가끔 학생들이 실수를 했던 문제입니다. 평균을 구하는 문제이므로

5개의 net change을 모두 더한 후 반드시 5로 나누어 주면 됩니다.

: 정답은 (C) :



26. If the average (arithmetic mean) of 5 positive temperatures is x degrees Fahrenheit, then the

sum of the 3 greatest of these temperatures, in degree Fahrenheit, could be

(A) x6 (B) x4 (C) 3

5x (D)

2

3x (E)

5

3x

xedcbaxedcba

5)(5)( =++++⇒=++++ 에서 cba ++ 의 최대값을 구하라는 문제네요.

일단 d 와 e 가 둘 다 0도(최소값, 실제 최소값은 0이 될 수 없지만 다만 식을 위해

0이라고 가정함)일 때를 오른쪽 식에 xedcba 5)( =++++ 에 대입하면 cba ++ <

x5 을 유도할 수 있습니다. 즉 cba ++ 의 범위는 x5 보다 작다는 것을 구할 수 있는

셈이네요. x5 보다 작으면서 가장 큰 값은 (B)입니다.

: 정답은 (B) :

Score Number of

Students

83 5

70 6

92 3

5

64 1

27. The incomplete table above shows a distribution of scores for a class of 20 students. If the

average (arithmetic mean) score for the class is 78, what score is missing from the table?

(A) 73 (B) 75 (C) 77 (D) 79 (E) 81

20 students × 78( average) = 15×60 = 83×5 + 70×6 + 92×3 + x ×5 + 64×1

773855 =→= xx

: 정답은 (C) :

28. If x is the average (arithmetic mean) of 5 consecutive even integers, which of the following

must be true?

I. x is an even integer.

II. x is a nonzero integer.

III. x is a multiple of 5.

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

(E) I, II, and III

가장 작은 even integer을 n 이라 하면 45

)8()6()4()2(+=

++++++++= n

nnnnnx

즉 4+= nx , 여기서 n 은 항상 짝수이므로 “짝수 + 짝수 = 짝수”이므로 I 은 항상

true입니다. II에서는 n = -4이면 false입니다.

: 정답은 (A) :



29. The average (arithmetic mean) of 4 positive integers is 50. If the average of 2 of these

integers is 45, what is the greatest possible value that one of the other 2 integers can have?

(A) 55

(B) 65

(C) 100 (D) 109

(E) 115

4개의 양의 정수의 평균이 50이면 합은 200입니다. 그 중에 두 정수의 평균이 45이므로 이

두 정수의 합은 90이 되네요. 전체 합 200에서 90을 빼면 110이 되고 나머지 두 정수

중에서 최대값은 모든 정수가 0이 아닌 정수라 했으므로 나머지 정수가 1인 경우 최대값이

되죠. 따라서 110 − 1 = 109

ÿ 정답은 (D)

30. The trade name for a product has 6 letters , and the length of the package for the product is

l centimeters. The trade name of the product is printed lengthwise on one side of the

package with a margin of m centimeters on each end of the side. If the space between each

letter is considered negligible, what is the average (arithmetic mean) width, in centimeters, of

each letter in the trade name?

(A) m2−l (B) m−l (C) 8÷l (D) 6)( ÷− ml (E) 6)2( ÷− ml

m m

l

각 글자의 평균 width = ( ml 2− ) ÷ 6

ÿ 정답은 (E)

GRE Math 강좌 Set 3

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