请教两题GWD，求过程

cxks01

Last Sunday a certain store sold copies of Newspaper A for $1.00 each and copies of Newspaper B for $1.25 each, and the store sold no other newspapers that day.If r percent of the store’s revenues from newspaper sales was from Newspaper A and if p percent of the newspapers that the store sold were copies of newspaper A, which of the following expresses r in terms of p?
A.100p / (125 – p)
B.150p / (250 – p)
C.300p / (375 – p)
D.400p / (500 – p)
E.500p / (625 – p)


VERBAL:

In the past the country of Siduria has relied heavily on imported oil.Siduria recently implemented a program to convert heating systems from oil to natural gas.Siduria already produces more natural gas each year than it burns, and oil production in Sidurian oil fields is increasing at a steady pace.If these trends in fuel production and usage continue, therefore, Sidurian reliance on foreign sources for fuel should decline soon.


Which of the following is an assumption on which the argument depends?

1. In Siduria the rate of fuel consumption is rising no more quickly than the rate of fuel production.
   
2. Domestic production of natural gas is rising faster than is domestic production of oil in Siduria.
   
3. No fuel other than natural gas is expected to be used as a replacement for oil in Siduria.
   
4. Buildings cannot be heated by solar energy rather than by oil or natural gas.
   
5. All new homes that are being built will have natural-gas-burning heating systems.
   为什么不是选E？
   

In the past the country of Siduria has relied heavily on imported oil.Siduria recently implemented a program to convert heating systems from oil to natural gas.Siduria already produces more natural gas each year than it burns, and oil production in Sidurian oil fields is increasing at a steady pace.If these trends in fuel production and usage continue, therefore, Sidurian reliance on foreign sources for fuel should decline soon.


Which of the following is an assumption on which the argument depends?

1. In Siduria the rate of fuel consumption is rising no more quickly than the rate of fuel production.
   
2. Domestic production of natural gas is rising faster than is domestic production of oil in Siduria.
   
3. No fuel other than natural gas is expected to be used as a replacement for oil in Siduria.
   
4. Buildings cannot be heated by solar energy rather than by oil or natural gas.
   
5. All new homes that are being built will have natural-gas-burning heating systems.
   为什么不是选E？
   

酸菜鱼315

1.根据题意，两个等式r*(A+1.25B)=A
                                 A/(A+B)=P
2.我觉得是这样，即使所有new homes都是natural-gas-burning heating systems，可是如果old homes对于fuel的消耗都快速增长，那么reliance on foreign sources for fuel还是会增长。

cxks01

还有这两题，求思路。读不太懂题目，特别第二题。第一题的话7选1和10选2，意思是一共17个人还是一共10个人，如果一共17个人，那none of the candidates is eligible for a position in both departments这个条件有什么用？
1.A certain university will select 1 of 7 candidates eligible to fill a position in the mathematics department and 2 of 10 candidates eligible to fill 2 identical positions in the computer science department.If none of the candidates is eligible for a position in both departments, how many different sets of 3 candidates are there to fill the 3 positions?

2.A total of 30 percent of the geese included in a certain migration study were male.If some of the geese migrated during the study and 20 percent of the migrating geese were male, what was the ratio of the migration rate for the male geese to the migration rate for the female geese?
[Migration rate for geese of a certain sex = (number of geese of that sex migrating) / (total number of geese of that sex)]


2.A total of 30 percent of the geese included in a certain migration study were male.If some of the geese migrated during the study and 20 percent of the migrating geese were male, what was the ratio of the migration rate for the male geese to the migration rate for the female geese?
[Migration rate for geese of a certain sex = (number of geese of that sex migrating) / (total number of geese of that sex)]