SAT数学重要知识点及例题

2016-10-18 10:41

1. 代数题

(1). Karl bought x bags of red marbles for y dollars per bag, and z bag of blue marbles for 3y dollars per bag. If he bought twice as many bags of blue marbles as red marbles, then in terms of y, what was the average cost, in dollars, per bag of marbles?

(A) (B) (C) 3x-y (D) 2y (E) 6y

(2). At this bake sale, Mr. Right sold 30% of his pies to one friend. Mr. Right then sold 60% of the remaining pies to another friend. What percent of his original number of pies did Mr. Right

have left?

(A) 10% (B) 18% (C) 28% (D) 36% (E) 40%

(3) At a track meet, 2/5 of the first-place finishers attended Southport High School, and 1/2 of them were girls. If 2/9 of the first-place finishers who did NOT attend Southport High School were girls, what fractional part of the total number of first-place finishers were boys?

(A) 1/9 (B) 2/15 (C) 7/18 (D) 3/5 (E) 2/3

2. 中位数

(4)Number of siblings per student in a preschool class

Number of siblings Number of Students

0 3

1 6

2 2

3 1

The table above shows how many students in a class of 12 preschoolers had 0,1,2, or 3 siblings. Later, a new student joined the class, and the average (arithmetic mean) number of siblings per student became equal to the median number of siblings per student. How many siblings did the new student have?

A. 0 B. 1 C. 2 D. 3 E. 4

(5)In a set of eleven different numbers, which of the following CANNOT affect the value of the median?

A. Doubling each number

B. Increasing each number by 10

C. Increasing the smallest number only

D. Decreasing the largest number only

E. Increasing the largest number only

(6). The least and greatest numbers in a list of 7 real numbers are 2 and 20, respectively. The median of the list is 6, and the number 3 occurs most often in the list. Which of the following could be the average (arithmetic mean) of the numbers in the list?

I. 7 II. 8.5 III. 10

A. I only

B. I and II only

C. I and III only

D. II and III only

E. I, II and III

3. 集合部分

(6) Set F consist of all of the prime numbers from 1 to 20 inclusive, and set G consist of all of the odd numbers from 1 to 20 inclusive. If f is the number of values in set F, g is the number of values of in Set G, and j is the number of values in F∪G, which of the following gives the correct value of f(j-g)?

A. 4 B. 8 C. 10 D. 11 E. 18

(7) Set X has x members and set Y has y members. Set Z consists of all members that are in either Set X or Set Y with the exception of the k common members (k>0). Which of the following represents the number of members in set Z?

A. x+y+k B. x+y-k C. x+y+2k D. x+y-2k E. 2x+2y-2k

(8) Of the 240 campers at a summer camp, 5/6 could swim, if 1/3 of the campers took climbing lessons, what was the least possible number of campers taking climbing lessons who could swim?

A. 20 B.40 C. 80 D.120 E. 200

(9)Set F consist of all of the prime numbers from 1 to 20 inclusive, and set G consist of all of the odd numbers from 1 to 20 inclusive. If f is the number of values in set F, g is the number of values of in Set G, and j is the number of values in F∪G, which of the following gives the correct value of f(j-g)?

A. 4 B. 8 C. 10 D. 11 E. 18

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