GWD数学难题请教~不知道是不是答案印错了。。。。。

烧饼的梦

Q14:  

How many seconds will it take for a car that is traveling at a constant rate of 45 miles per hour to travel a distance of 22 yards?    (1 mile = 1,160 yards)



A.     8

B.     9

C.     10（答案）

D.     11

E.      12
我做的是约等于1.5s
Q8:

           Note:  Figure not drawn to scale.

图形为一个正方形，三横把正方形平分,每份宽3，三竖不均等但距两边长度相等设为x，中间为白色，几块黑白相间

The figure above represents a square garden that is divided into 9 rectangular regions with indicated dimensions in meters.  The shaded regions are planted with peas, and the unshaded regions are planted with tomatoes.  If the sum of the areas of the regions planted with peas is equal to the sum of the areas of the regions planted with tomatoes, what is the value of x?



A.     0.5

B.     1

C.     1.5（答案）

D.     2

E.      2.5
我算的是2.25
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（答案）

E.      9
我算的是10
Q19:

At a certain company, 25 percent of the employees are male and 50 percent of the employees are sales staff.  What is the number of employees at this company?

(1)     Exactly 7 of the employees at the company are males who are sales staff.

(2)     There are 16 more female employees than male employees at the company.
答案为b，为什么 不能选d呢？
Q2:

If 2 different representatives are to be selected at random from a group of 10 employees and if p is the probability that both representatives selected will be women, is p >1/2 ?

(1)     More than 1/2 of the 10 employees are women.

(2)     The probability that both representatives selected will be men is less than1/10 .
答案为e,为什么不能选b?

Q28:

This year Henry will save a certain amount of his income, and he will spend the rest.  Next year Henry will have no income, but for each dollar that he saves this year, he will have 1 + r dollars available to spend.  In terms of r, what fraction of his income should Henry save this year so that next year the amount he was available to spend will be equal to half the amount that he spends this year?




A.  1/(r+2)  
B.     1/(2r+2)
C.     1/(3r+2)
D.  1/(r+3)
E.   1/(2r+3)(答案)
看不懂题目。。。。

Q9:

If an integer n is to be chosen at random from the integers 1 to 96, inclusive, what is the probability that n(n + 1)(n + 2) will be divisible by 8?



A.     1/4

B.     3/8

C.     1/2

D.     5/8（答案）

E.      3/4
不会算。。。。
Q16:

What is the probability that a student randomly selected from a class of 60 students will be a male who has brown hair?

(1)     One-half of the students have brown hair.

(2)     One-third of the students are males.
答案e，为什么啊?这类题不选c，是因为少了什么条件吗？

烧饼的梦

第二题的图弄不上去。。。。怎么办。。。。？谁能教教我？

catling

Q14.  ~1.5s

Q16. Shaded area = 4*3*x + (9-2x)*3  ==  Unshaded = 2*3*x + 2*(9-2x)*3
        =>  6x = 18-6x => x=1.5

Q22.
 直接硬解
       A0  B3  - 1  
       A1  B2  - 3
       A2  B1  - 3
       A3  B0  - 1
合计8. 貌似有个公式可以直接算的, 不过不记得了.

Q19
已知  male = 0.25*total,  sale = 0.5*total
1)  number of (male & sale) = 7  ==> 没提供任何关于 male, sale, or total 的消息
2）注意，男人的对面是女人啊
    female = 16 + male => 0.75*total = 16 + 0.25*total ==> 可解

Q2
假设其中有f个女生
p = [f*(f-1)/2!] / [10*9/2!] = f*(f-1)/90
1) f>5 => f=6,7,8,9,10  
     f=6, p = 1/3 不成立
2) (10-f)*(10-f-1)/90 < 1/10 => (10-f)*(9-f) < 9 => f = 7, 8, 9
     f = 7的时候，p = 42/90 < 0.5
答案是ｅ

catling

Q28
假设 s 为今年存下来的部分,  1-s 就是今年花掉的部分
存下来的部分第二年成为  s*(1+r)  =  1/2*今年的开销  = 1/2*(1-s)
 =>  s * (2r+3) = 1 => s = 1/(2r+3)

Q9
n=4k => 4k*(4k+1)*(4k+2)  divisible by 8   ==  1/4 概率
n=4k+1 => (4k+1)*(4k+2)*(4k+3)  not divisible by 8, only divisible by 2   ==  1/4概率
n=4k+2 => (4k+2)*(4k+3)*(4k+4)  divisible by 8   ==  1/4 概率
n=4k-1 => (4k-1)*4k*(4k+1), k为偶数的时候 divisible by 8  == 1/8概率
合计  1/4+1/8 = 5/8

Q16
这两个条件在一起提供不了解。举个例子，brown hair可以全是女生，也可以一半是女生，这都不矛盾，没办法求解。把条件列出来也很清楚
已知条件  male + female = 60
1) brown = 30
2) male = 20
没有任何关于 male&brown 的信息

烧饼的梦

谢谢呵呵~终于明白了~不过第二题，带图那个，我觉得那个等式左边对了，右边一约应该是（9-2x）*3 这样解得4x=9啊。。。

ggghost

Q22   2^3=8     没说different employee,只说了 different office 所以这题可以理解为  每次决定是给甲办公室加人 还是给乙办公室加人，有三轮决定权 ，所以就是 2的三次方

烧饼的梦

谢谢ggghost~我一开始当成可以不安排3人，一个人都不安排也行了。。。。不知道脑子怎么就进水了。。。。呵呵