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The average (arithmetic mean) of a set of seven numbers is 8

题目
单选题
The average (arithmetic mean) of a set of seven numbers is 81. If one of the numbers is discarded, the average of the remaining numbers is 78. What is the value of the number that was discarded?
A

98

B

99

C

100

D

101

E

102

参考答案和解析
正确答案： B
解析：
If the average (arithmetic mean) of a set of seven numbers is 81, then the sum of these seven numbers is 7 x 81 or 567. Since, if one of the numbers is discarded, the average of the six remaining numbers is 78, the sum of these six numbers is 6×78 or 468. Since 567 - 468 = 99, the value of the number that was discarded is 99.
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相似问题和答案

第1题：

187 The centerline of a standard "Shewhart' control chart represents:

A. the process target

B. the nominal dimension specified by the customer

C. the nominal dimension specified by the designer

D. the true process average or mean

E. the process sample average or mean


正确答案：E

第2题：

In a weather report GMT stands for ________ ．

A.Greenwich Mean Time

B.Local Mean Time

C.General Cargo

D.General Average


正确答案：A

第3题：

The centerline of a standard "Shewhart' control chart represents:

A . the process target

B . the nominal dimension specified by the customer

C . the nominal dimension specified by the designer

D . the true process average or mean

E . the process sample average or mean


正确答案：E

第4题：

单选题
What is the average (arithmetic mean) of 8 consecutive odd integers if the smallest of those integers is n?
A

n+5

B

n+6

C

n+7

D

n+8

E

n+9


正确答案： E
解析：
最小的整数为n。它们是连续的奇数。这组整数为:n,n+ 2, n+4, n+6, n+8, n+10, n+12, n+14。计算这些整数的平均数即为将它们想加除于8。得出（8n+56）/8=n+7

第5题：

The average height of the surface of the sea for all stages of the tide over a 19 year period is called ______.

A.mean high water

B.mean low water

C.half-tide level

D.mean sea level


正确答案：D

第6题：

Those numbers come to mean the world to you ()they give you the record of how much money you’ve earned or lost.

A、because

B、so that

C、in case


参考答案：A

第7题：

The height of a light is measured from which reference plane?

A.Mean low water

B.Mean high water

C.Average water level

D.Geographical sea level


正确答案：B

第8题：

The rule of seven used by quality control engineers states that if a run of seven or more samples lays on one side of the process mean, then the process is out of control. What is the probability that this condition is the result of random variations.

A . 14.30%

B . 3.12%

C . 2.73%

D . 1.56%

E . 0.78%


正确答案：D

第9题：

问答题
Kara attends a university where students study for an average (arithmetic mean) of 13.4 hours per week. How many hours per week does Kara study?　　(1) The standard deviation of study time at Kara’s school is 2.8.　　(2) Kara’s study time is one standard deviation away from the mean.

正确答案： E
解析：
（1）条件告诉了Kara学校学生学习时间的总标准差，无法计算Kara的学习时间数值；（2）条件指出Kara的学习时间距离平均数有两个标准差区间，不能确定其是高于还是低于平均值，故本题应选E项。

第10题：

单选题
The average (arithmetic mean) of c and d is 12, and the average of c, d, and e is 10. What is the value of e?
A

6

B

10

C

12

D

18

E

20


正确答案： A
解析：
根据题目中已知的数量关系，可列等式如下：c+d= 12×2=24……①；c+d+e=10×3=30……②。把等式①代入等式②得，24+e=30，e=6。

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