求救两道数学题（GWD的）

eliasfan

Q16:

If n is a positive integer and r is the remainder when (n-1)(n+1) is divided by 24, what is the value of r?

(1)2 is not a factor of n.

(2)3 is not a factor of n.



A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

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
D. 11
E. 12


Q14:

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)]

A.1/4

B.7/12

C.2/3

D.7/8

E.8/7

Answer:
这题思路是怎么样的？
求救啊！！！！

gavensc

恩，看来就是了

方法肯定没有错的。

xianyunfeng

题目错了，我上manhattan.com看过他们讨论。A和B的位置应该换换

eliasfan

确定没有抄错，这是GWD的原题
直接Copy过来的

gavensc

你确定你没又抄错题吧？

假设卖出a=100份（即使无所谓a是多少，最后能约掉）   那么有p/100 ×100=p份的报纸B卖掉， 然后卖掉的A报纸是100-p

那么总的revenue就是 1.25p+1*(100-p)=0.25p+100

r/100 * 【0.25p+100】 =1*(100-p)   解出来r就行了   但是貌似没有答案。

eliasfan

这题答案为D
也不知道是怎么来的

eliasfan

不过还有一道题麻烦帮忙看一下
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 B, 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)

eliasfan

谢谢gavensc

gavensc

我晕  1mile=1760yards

那么 45 miles per hour = 45×1760 / 3600 = 22 yard / second

然后 22/ 22 =1  

我算的是1 啊怎么 晕

gavensc

你第二题数对么，看着挺简单啊，我怎么算的是 44/29 秒， 我晕。