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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 6B 10C 12D 18E 20

题目
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

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更多“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 6B 10C 12D 18E 20”相关问题

  • 第1题：

    统计用区划代码的位数是（）。

    • A、6
    • B、10
    • C、12
    • D、17

    正确答案:C

  • 第2题：

    日内瓦印记共多少条法则？（）

    • A、6
    • B、10
    • C、12
    • D、20

    正确答案:C

  • 第3题：

    单选题
    The average of a, b, c, d, and e is 28. If the average of a, c, and e is 24, what is the average of b and d?
    A

    31

    B

    32

    C

    33

    D

    34

    E

    36


    正确答案： C
    解析：
    If the average of a, b, c, d, and e is 28, then (a + b + c + d + e)/5 = 28, or a + b + c + d + e=5×28= 140. If the average of a, c, and e is 24, then (a + c + e)/3 = 24. Or a + c + e= 3 × 24 = 72. Substituting 72 for a+c+e in a+b+c+d+e=140 gives b+d+72 = 140, b +d = 140－72 = 68, (b + D./2 = 68/2 = 34.

  • 第4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。

  • 第5题：

    问答题
    If 10a + 10b =35, what is the average (arithmetic mean) of a and b?

    正确答案： 1.75
    解析：
    由10a+10b=35可得10(a+b)=35→a+b=3.5，所以a和b的平均数是3.5÷2=1.75。

  • 第6题：

    问答题
    At the eating contest the winner ate an average of 15 hot dogs at the first 20 sittings. After a further 20 sittings the average increased to 20 hot dogs. What was the average for the last 20 sittings?

    正确答案： 25.
    解析：
    前20轮共吃汉堡300个，40轮下来共吃汉堡800个，则后20轮吃汉堡500个，因此每轮吃25个。

  • 第7题：

    单选题
    Click the Exhibit button. What is the result？（）
    A

    Value is： 8

    B

    Compilation fails.

    C

    Value is： 12

    D

    Value is： -12


    正确答案： D
    解析： 暂无解析

  • 第8题：

    问答题
    If a is an integer, is b an integer?　　(1) The average (arithmetic mean) of a and b is an integer.　　(2) The average (arithmetic mean) of a, b, and b+4 is a.

    正确答案： D
    解析：
    根据算数平均数的定义可知，本题应选D项。

  • 第9题：

    单选题
    The average (arithmetic mean) of five numbers is 10. The sum of three of the numbers is 30. What is the sum of the other two numbers?
    A

    5

    B

    10

    C

    20

    D

    30

    E

    40


    正确答案： C
    解析：
    The arithmetic mean of the five numbers is 10. That means the sum of the numbers is 50. The sum of three numbers is 30. so the sum of the remaining two numbers is 50-30 = 20.

  • 第10题：

    单选题
    For integer values of the age from 10 months to 14 months, the average (arithmetic mean) weight falls approximately between ______ pounds.
    A

    750 and 850

    B

    850 and 950

    C

    950 and 1050


    正确答案： C
    解析：
    在10个月时，大象的体重大约为800磅，到了14个月大象的体重大约为1000磅，在这期间大象的体重变化比较平稳，因此体重平均数大约为900磅，故答案选B。

  • 第11题：

    单选题
    The average (arithmetic mean) of x and y is m, where m ≠ 0. What is the average (arithmetic mean) of x, y, and 2m?
    A

    m

    B

    4/3m

    C

    3/2m

    D

    5/3m

    E

    2m


    正确答案： D
    解析：
    因为x和y的算术平均数为m，所以x+y=2m，所以，所以x,y,2m的算术平均数为x+y+2m/3，因为x + y = 2m，所以x+y+2m/3=4m/3

  • 第12题：

    问答题
    What is the average (arithmetic mean) of x and y?　　(1) The average of x+3 and y+5 is 14.　　(2) The average of x,y and 16 is 12.

    正确答案： D
    解析：
    将两条件分别代入计算可知，x和y的平均数均为10，故本题选D项。

  • 第13题：

    四环素的有效血浓度维持约多少小时？（）

    • A、4～6
    • B、8～10
    • C、12～14
    • D、16～18
    • E、20～22

    正确答案:B

  • 第14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15题：

    单选题
    If the average of 8 and x is 10 and the average of 7 and y is 11, what is the average of x and y?
    A

    9.0

    B

    10.5

    C

    12.0

    D

    13.5

    E

    15.00


    正确答案： C
    解析：
    因为8和x的平均数为10，可得出(8+x)/2=10，x=12。又因为7和y的平均数为11，所以可得出7 + y = 22，y=15，所以x和y的平均值为(x+y)/2=(12+15)/2= 27/2=13.5。

  • 第16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： D
    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17题：

    问答题
    At the beer-drinking contest the winner drank an average of 10 bottles of beer at the first 20 rounds. After a further 20 rounds the average increased to 15 bottles. What is the average for the last 20 rounds?

    正确答案： 20.
    解析：
    在前20轮中胜者平均喝10瓶酒，共喝200瓶。再过20轮后平均喝15瓶，即共喝了40×15=600瓶。故，后20轮喝了400瓶，胜者平均喝20瓶。

  • 第18题：

    单选题
    If 70% of the bananas in a particular harvest had an average (arithmetic mean) length of 7 inches and 30% of the bananas in that harvest had an average (arithmetic mean) length of 5 inches, what was the average (arithmetic mean) length, in inches, of all of the bananas in the harvest?
    A

    6.0

    B

    6.2

    C

    6.4

    D

    6.6

    E

    6.8


    正确答案： B
    解析：
    假设共有100个香蕉，根据题干全部香蕉的长度为(100×70%×7)+(100×30%×5)=640英尺，共有100只香蕉，所以平均每只香蕉的长度为640/100=6.4。故选C。

  • 第19题：

    单选题
    If the set S is composed of the following numbers {99, 100, 100, 105, 106, 116, 123}, which of the following is largest?
    A

    The average (arithmetic mean) of set S

    B

    The median of set S

    C

    The mode of set S

    D

    The range of set S

    E

    The standard deviation of set S


    正确答案： B
    解析：
    根据公式可知，A项S数集的平均数=107，B项S数集的中位数=105，C项S数集的众数=100，D项S数集的极差=24，E项S数集的标准差≈9，故本题选A项。

  • 第20题：

    问答题
    If M is a set of five numbers p, q, r, s and t, is the range of numbers in M greater than 5?　　(1) The average (arithmetic mean) of p, q, r, S, and t is 5.　　(2) p-r>5.

    正确答案： B
    解析：
    条件1不能判断M数集的极差；由p-r>5可知p、r间的距离大于5，故M的极差大于5，所以本题应选B项。

  • 第21题：

    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


    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.

  • 第22题：

    单选题
    If the average (arithmetic mean) of 3, 7, 10, and x is 7, then what is the median of 3,7,10, and x?
    A

    5.5

    B

    6

    C

    6.5

    D

    7

    E

    7.5


    正确答案： D
    解析：
    因为3,7,10,和x 的平均数是7，可得出等式(3+7+10+x)/4=7，(20 + x)/4= 7，20+ x = 28，x = 8。所以3,7,10,和x四个数排序为3,7,8,10，它们的中位数为(7+8)/2=7.5。

  • 第23题：

    单选题
    If the average (arithmetic mean) of a, b, 4, and 10 is 8, what is the value of a + b?
    A

    4

    B

    6

    C

    9

    D

    15

    E

    18


    正确答案： B
    解析：
    根据题干可得出(a+ b + 10 + 4)/4=8，a + b=18。

  • 第24题：

    问答题
    MegaTech and UltraCorp are considering a merger to form the MegaUltraTech Corporation. Does MegaTech have more employees than UltraCorp?　　(1) The average (arithmetic mean) age of UltraCorp employees is 32.8, while the average age of MegaTech employees is 27.2.　　(2) If the merger goes through and all employees from both companies remain employed, the average (arithmetic mean) age of the MegaUltraTech employees will be 31.4.

    正确答案： C
    解析：
    条件1、2中均不涉及两个公司的员工数量，但是将两者综合可以推断出UltraCorp的员工数大于MegaTech，故本题选C项。

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