2011 AMC 10B 第 2 题

Question

Josanna 到目前为止的考试分数为

90

、

80

、

70

、

60

和

85

。她的目标是在下一次考试后把考试平均分至少提高

3

分。她至少需要在下一次考试中得到多少分？

Josanna’s test scores to date are

90,

80,

70,

60,

and

85.

Her goal is to raise her test average at least

3

points with her next test. What is the minimum test score she would need to accomplish this goal?

80

82

85

90

95

求当前总分和目标平均分。

Find the current total score and target average

第六次考试后总分必须达到

6\cdot80

。

The sixth score must bring the total to

6\cdot80

她当前的平均分为

\dfrac{90+80+70+60+85}5 = 77\text{，}

而总分为

385

。目标平均分为

80

，所以六次考试所需的总分为

80\cdot 6

。因此下一次考试至少需要得

80\cdot 6-385 = 95\text{。}

所以正确答案是 E。

Her current average is

\dfrac{90+80+70+60+85}5 = 77,

and the sum of her scores is

385.

The desired average is then

80,

so the sum of scores required is

80\cdot 6.

Therefore, the answer is

80\cdot 6-385 = 95.

Thus, the correct answer is E .

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