ACT数学备考资料大全

ACT数学备考资料大全具体如下：

1. 3x3?2x2y?4x2y is equivalent to:

A. 9x7y2

B. 9x12y2

C. 24x7y2

D. 24x12y

E. 24x12y2

解析：The correct answer is C. To find an equivalent expression, you can multiply the constants (3?2?4)， combine the x term (x3x2x2 → x3+2+2 → x7, because when you have a common base you use the base and add the exponents)， and combine the y terms (y?y → y1y1 → y1+1 → y2)。 The result is 24x7y2.

正确答案选C。常数相乘(3?2?4)，合并x项(x3x2x2 → x3+2+2 → x7) 和y项(y?y → y1y1 → y1+1→ y2)，结果为24x7y2。

2. Mr. Dietz is a teacher whose salary is $22,570 for this school year, which has 185 days. In Mr. Dietz's school district, substitute teachers are paid $80 per day. If Mr. Dietz's takes a day off without pay and a substitute teacher is paid to teach Mr. Dietz's classes, how much less does the school district pay in salary by paying a substitute teacher instead of paying Mr. Dietz's for that day?

F. $ 42

G. $ 80

H. $ 97

J. $105

K. $122

解析：The correct answer is F. To find Mr. Dietz's pay per day, you can divide his salary, $22,570, by the number of days he works,185. His pay per day is 22570/185, or $122. When Mr. Dietz takes a day off without pay and the school pays a subsititute $80, the school district saves the difference in these amounts, 122-80, or $42.

正确答案选F。先算出Dietz先生每天的平均工资，用22570除以185(可用计算器)，即122美元。再用122美元减去学校需要支付临时老师的费用80美元，即可算出学校结余的费用，为42美元。

3. So far, a student has earned the following scores on four 100-point tests this grading period:65,73,81, and 82. What score must the student earn on the fifth and last 100-point test of the grading period to earn an average test grade of 80 for the 5 tests?

A. 75

B. 76

C. 78

D. 99

E. The student cannot earn an average of 80.

解析：The correct answer is D. To find what the student needs to score on the fifth 100-point test to average a score of 80, you need to find the point total for the student so far by adding 65,73, 81 and 82. That sum is 301. Averaging 80 points on 5 tests means the student must earn 400 points (80?5)。 The acore needed on the last test is the difference,400～301, or 99.

正确答案选D。该学生前四次共得301分;5次考试平均分为80，意味着5次考试总分需达到400分，那么该学生最后一次考试需要达到的分数为400与301的差，即99分。