【官方指南】新GRE数学真题OG例题讲解之数列找规律

8.Frequency Distribution for List X

Number            1  2  3  5

Frequency          10 20  18 12

Frequency Distribution for List Y

Number            6  7  8  9

Frequency          24 17 10  9

List X and list Y each contain 60 numbers. Frequency distributions for each list are given above. The average (arithmetic mean) of the numbers in list X is 2.7, and the average of the numbers in list Y is 7.1. List Z contains 120 numbers: the 60 numbers in list X and the 60 numbers in list Y.

Quantity A                              Quantity B

The average of the 120numbers in list Z  The median of the 120 numbers in list Z

9.The figure above shows the graph of the function f in the xy-plane. What is the value of f ( f (–1)) ?

A –2

B –1

C 0

D 1

E 2

10.By weight, liquid A makes up 8 percent of solution R and 18 percent of solution S. If 3 grams of solution R are mixed with 7 grams of solution S, then liquid A accounts for what percent of the weight of the resulting solution?

A 10%

B 13%

C 15%

D 19%

E 26%

11.Of the 700 members of a certain organization, 120 are lawyers. Two members of the organization will be selected at random. Which of the following is closest to the probability that neither of the members selected will be a lawyer?

A 0.5

B 0.6

C 0.7

D 0.8 E 0.9

12.Line k lies in the xy-plane. The x-intercept of line k is –4, and line k passes through the midpoint of the line segment whose endpoints are (2, 9) and (2, 0). What is the slope of line k ?

Give your answer as a fraction._______

13.In the course of an experiment, 95 measurements were recorded, and all of the measurements were integers. The 95 measurements were then grouped into 7 measurement intervals. The graph above shows the frequency distribution of the 95 measurements by measurement interval.

Quantity A                             Quantity B The average (arithmetic                   The median of the 95 mean) of the 95                          measurements

Measurements

14.The random variable X is normally distributed. The values 650 and 850 are at the 60th and 90th percentiles of the distribution of X, respectively.

Quantity A                              Quantity B The value at the 75th                       750 percentile of the distribution of X

15.If 1+x+x2+x3=60, then the average (arithmetic mean) of x, x2, x3, and x4 is equal to which of the following?

A 12x

B 15x

C 20x

D 30x

E 60x