2015年ACT考試數學習題及解析（3）

　　網ACT測驗頻道小編為考生們匯集了ACT測驗數學演習題，快快練起來吧!

　　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.

　　剖析：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.

　　準確謎底選D。該門生前四次共得301分;5次測驗均勻分為80，象征著5次測驗總分需到達400分，那末該門生末了一次測驗須要到達的分數為400與301的差，即99分。