3x3·2x2y·4x2y is equivalent to:
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。
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
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.
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?
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.