三道SAT数学练习题及答案

SAT数学题拥有自己的逻辑关系和解题方法，这些都是大家在备考的时候，需要格外注意的部分。下面我们一起来看看这些数学题的详细内容吧。

Read the following SAT test question and then click on a button to select your answer.

1、A jar contains only red marbles and green marbles. If a marble is selected at random from the jar, the probability that a red marble will be selected is . If there are 36 green marbles in the jar, how many red marbles are there in the jar?

Answer Choices

(A) 18

(B) 24

(C) 54

(D) 72

(E) 108

2、In the , line is perpendicular to the graph of the function . Line could be the graph of which of the following functions?

Answer Choices

(A)

(B)

(C)

(D)

(E)

3、A special lottery is to be held to select the student who will live in the only deluxe room in a dormitory. There are seniors, juniors, and sophomores who applied. Each senior's name is placed in the lottery times; each junior's name, times; and each sophomore's name, time. What is the probability that a senior's name will be chosen?

Answer Choices

(A)

(B)

(C)

(D)

(E)

Explanation

1、The correct answer is D

Choice (D) is correct. Let r be the number of red marbles in the jar. The probability of selecting a red marble is equal to the number of red marbles divided by the total number of marbles. Since the probability of selecting a red marble is , it follows that . There are 36 green marbles and r red marbles, so the previous equation becomes . This simplifies to2(r + 36) = 3r, or 2r + 72 = 3r. Therefore, the number of red marbles, r, is 72.

2、The correct answer is B

If two lines are perpendicular, the product of their slopes is equal to . The function is in slope-intercept form, so the slope of the graph of is equal to . Therefore, the slope of line must be equal to . The only choice that corresponds to a slope of is .

3、The correct answer is D

To determine the probability that a senior's name will be chosen, you must determine the total number of seniors' names that are in the lottery and divide this number by the total number of names in the lottery. Since each senior's name is placed in the lottery times, there are seniors' names. Likewise, there are juniors' names and sophomores' names in the lottery. The probability that a senior's name will be chosen is .