2. 外语
  3. Ellen has received the following scores on 3 exams: 82, 74, and 90. What score will Ellen need to receive on the next exam so th

Ellen has received the following scores on 3 exams: 82, 74, and 90. What score will Ellen need to receive on the next exam so th

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问题 Ellen has received the following scores on 3 exams: 82, 74, and 90. What score will Ellen need to receive on the next exam so that the average(arithmetic mean)score for the 4 exams will be 85?
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答案94
解析 Let x represent the score on Ellens next exam. This initial step of assigning a variable to the quantity that is sought is an important beginning to solving the problem. Then in terms of x, the average of the 4 exams is

which is supposed to equal 85. Now simplify the expression and set it equal to 85:

Solving the resulting linear equation for x, you get
246 + x = 340
x = 94
Therefore, Ellen will need to attain a score of 94 on the next exam.
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