[求助]GWD 6 三道题不会 （求助）

yang8630

GWD 6

    

Q3: （这题不会算，我开始用10* 8* 6去算=480一看没选项，很晕！！！）

    

If a committee of 3
people is to be selected from among 5 married couples so that the committee
does not include two people who are married to each other, how many such committees
        （是问的这个组合）are possible?

    

 

    

A.    20

    

B.     40

    

C.     50

    

D.    80

    

E.     120

    

Answer: D

    

 

    

Q9: （这题看似简单，但只能求出一个半径的范围，求不出具体值啊）

    

In the xy-plane,
the point (-2, -3) is the center of a circle. 
The point (-2, 1) lies inside the circle and the point (4, -3) lies
outside the circle.  If the radius r of the circle is an integer, then r =

    

 

    

A.    6

    

B.     5

    

C.     4

    

D.    3

    

E.     2

    

Answer: B

    

Q30:  （应该是A，但怎么可以推出呢，不能考场上一个数一个数的试阿）

    

Joanna bought only $0.15 stamps and $0.29 stamps.  How many $0.15 stamps did she buy?

    

(1)
          She bought $4.40 worth of
stamps.

    

(2)
          She bought an equal number
of $0.15 stamps and $0.29 stamps.

Answer: A

[此贴子已经被作者于2008-10-16 5:51:38编辑过]

kingtom

以下是引用yang8630在2008-10-16 5:51:00的发言：

GWD 6

 

Q3: （这题不会算，我开始用10* 8* 6去算=480一看没选项，很晕！！！）

 

If a committee of 3
people is to be selected from among 5 married couples so that the committee
does not include two people who are married to each other, how many such committees
  （是问的这个组合）are possible?

 

 

A.    20

 

B.     40

 

C.     50

 

D.    80

 

E.     120

 

Answer: D

先从5对夫妇中选出3对共C3-5，再从3对中各选一个人，乘法原理C3-5*2^3=10*8=80
 

 

Q9: （这题看似简单，但只能求出一个半径的范围，求不出具体值啊）

 

In the xy-plane,
the point (-2, -3) is the center of a circle. 
The point (-2, 1) lies inside the circle and the point (4, -3) lies
outside the circle.  If the radius r of the circle is an integer, then r =

 

 

A.    6

 

B.     5

 

C.     4

 

D.    3

 

E.     2

 

Answer: B

求出两点到圆心的距离，很简单，一个是4一个是6，4和6之间只有一个整数5。 

Q30:  （应该是A，但怎么可以推出呢，不能考场上一个数一个数的试阿）

 

Joanna bought only $0.15 stamps and $0.29 stamps.  How many $0.15 stamps did she buy?

 

(1)
    She bought $4.40 worth of
stamps.

 

(2)
    She bought an equal number
of $0.15 stamps and $0.29 stamps.

Answer: A

这题我也没有别的办法，我估计只能硬算，但是其实也不需要试很多数，因为想被15整除，尾数必须是5或0，所以29分的张数只能是5，10，15，超过20就超过总数了，所以只需要是三个数即可。