[求助]几道不知道思路的数学题(尚未解决！）

Q11:

On Saturday morning, Malachi will begin a camping vacation and he will return home at the end of the first day on which it rains.  If on the first three days of the vacation the probability of rain on each day is 0.2, what is the probability that Malachi will return home at the end of the day on the following Monday?

A.    0.008

B.     0.128

C.     0.488

D.    0.512

E.     0.640

已经解决

Q22:

A certain company assigns employees to offices in such a way that some of the offices can be empty and more than one employee can be assigned to an office.  In how many ways can the company assign 3 employees to 2 different offices?

A.    5

B.     6

C.     7

D.    8

E.     9

已经解决

A.    10/189

B.     15/196

C.     16/225

D.    25/144

E.     39/128

Q10:

A certain quantity is measured on two different scales, the R-scale and the S-scale, that are related linearly.  Measurements on the R-scale of 6 and 24 correspond to measurements on the S-scale of 30 and 60, respectively.  What measurement on the R-scale corresponds to a measurement of 100 on the S-scale?

A.    20

B.     36

C.     48

D.    60

E.     84

已经解决

已经解决

Q33:

A photographer
   will arrange 6 people of 6 different heights for photograph by placing them in two rows of three so that each person in the first row is standing in front of someone in the second row.  The heights of the people within each row must increase from left to right, and each person in the second row must be taller than the person standing in front of him or her.  How many such arrangements of the 6 people are possible?

                                    A.    5

                                    A.    5

                                    A.    5

B.     6

C.     9

D.    24

E.     36

A.    36.00 sq cm

B.     35.00 sq cm

C.     33.75 sq cm

D.    30.25 sq cm

E.     25.00 sq cm

Q2:

A certain characteristic in a large population has a distribution that is symmetric about the mean m.  If 68 percent of the distribution lies within one standard deviation d of the mean, what percent of the distribution is less than m +
    d ?

A.    16%

B.     32%

C.     48%

D.    84%

E.     92%

Q1:

If the probability is 0.54 that Stock A will increase in value during the next month and the probability is 0.68 that Stock B will increase in value during the next month, what is the greatest possible value for the probability that neither of these two events will occur?

A  0.22

B  0.32

C    0.37

D   0.46

E.    0.63

11.0.8*0.8*0.2=0.128

12.2*2*2=8

15.题目看不懂，不好意思

15题：下面那个数是有限小数

选128那个

谢谢楼上2位！

11题的来由：是不是说按照人来算，每个人都有2个选择，去A部门或者去B部门，所以3个人就是2X2X2了？

15题是根据什么来判断的？还请明示！谢谢

15.128是2的几次幂，所以一定是有限小数

10.再次题目看不懂

23.应该还要乘以2，因为两面皆可么

33.最高最矮的人位置是固定的，其余四个人排列，设为A,B,C,D,身高升序，共有5种排法

C,D     B,D     B,C     A,D    A,C

  A,B     A,C     A,D     B,C    B,D

Q11:

On Saturday morning, Malachi will begin a camping vacation and he will return home at the end of the first day on which it rains.  If on the first three days of the vacation the probability of rain on each day is 0.2, what is the probability that Malachi will return home at the end of the day on the following Monday?

A.    0.008

B.     0.128

C.     0.488

D.    0.512

E.     0.640

已经解决

0.8*0.8*0.2=0.128

Q22:

A certain company assigns employees to offices in such a way that some of the offices can be empty and more than one employee can be assigned to an office.  In how many ways can the company assign 3 employees to 2 different offices?

A.    5

B.     6

C.     7

D.    8

E.     9

已经解决

2个office人数分别为a和b,有以下情况:

a=0  b=3   这里可能性只有1

a=1  b=2   这里可能性有3(a中可以是3人中任一个)

a=2  b=1   这里可能性有3(b中可以是3人中任一个)

a=3  b=0   这里可能性只有1

共1+3+3+1=9种

A.    10/189

B.     15/196

C.     16/225

D.    25/144

E.     39/128

E的分母=2*2*2*2*2*2*2所以该分数等于有尽小数

Q10:

A certain quantity is measured on two different scales, the R-scale and the S-scale, that are related linearly.  Measurements on the R-scale of 6 and 24 correspond to measurements on the S-scale of 30 and 60, respectively.  What measurement on the R-scale corresponds to a measurement of 100 on the S-scale?

A.    20

B.     36

C.     48

D.    60

E.     84

 2个scale之间的对应是线形关系,可列等式Y=aX+b  其中X是R-scale上的任意数,Y是S-scale上的对应数,a,b是常数.根据条件列等式:

30=6a+b

60=24a+b

计算得出a=5/3,b=20

当Y=100时,X=48,得解.

 2个scale之间的对应是线形关系,可列等式Y=aX+b  其中X是R-scale上的任意数,Y是S-scale上的对应数,a,b是常数.根据条件列等式:

30=6a+b

60=24a+b

计算得出a=5/3,b=20

当Y=100时,X=48,得解.

When tossed, a certain coin has equal probability of landing on either side.  If the coin is tossed 3 times, what is the probability that it will land on the same side each time?

A.    1/8

B.     1/4

C.     1/3

D.    3/8

E.     1/2

按我原来以为，应该是三个1/2的连乘，但是答案说是B?

 1/2*1/2*1/2*2=1/4   有正反面2种可能,所以还要*2

 1/2*1/2*1/2*2=1/4   有正反面2种可能,所以还要*2

A photographer
   will arrange 6 people of 6 different heights for photograph by placing them in two rows of three so that each person in the first row is standing in front of someone in the second row.  The heights of the people within each row must increase from left to right, and each person in the second row must be taller than the person standing in front of him or her.  How many such arrangements of the 6 people are possible?

A.    5

B.     6

C.     9

D.    24

E.     36

这个排列比较复杂，不知道如何理清，请指点。

 这个数量比较少我还是用列举法.

按身高把人列为1-6,6最高.根据条件判断1在第一排左一,6在第二排左三.(因为反之不可能)

第一排左二必须有三个数大于它.(第一排左三,第二排左二和第二排左三6),所以只有2,3两种可能.

当第一排左二为2时,第一排左三有3,4,5三种可能;当第一排左二为3时,第一排左三有4,5两种可能.

共五种.

 这个数量比较少我还是用列举法.

按身高把人列为1-6,6最高.根据条件判断1在第一排左一,6在第二排左三.(因为反之不可能)

第一排左二必须有三个数大于它.(第一排左三,第二排左二和第二排左三6),所以只有2,3两种可能.

当第一排左二为2时,第一排左三有3,4,5三种可能;当第一排左二为3时,第一排左三有4,5两种可能.

共五种.

谢谢楼上！

不过这个算术似乎不对吧？呵呵1+3+3+1=8，不是9.莫非你的键盘和我一样，我是8和7这2个数字键居然是装反了的，所以错无数次才发现原来是装错了。

是8，打错了。。。见笑啦