PREP1--两题求助!!-----急!!----大家请帮忙

exhilarating

两题目没太懂意思...
90. (D)
On Jane's credit card account, the average daily balance for a 30-day billing cycle is the average (arithmetic mean) of the daily balances at the end of each of the 30 days.  At the beginning of a certain 30-day billing cycle, Jane's credit card account had a balance of $600.  Jane made a payment of $300 on the account during the billing cycle.  If no other amounts were added to or subtracted from the account during the billing cycle, what was the average daily balance on Jane's account for the billing cycle?
(1)  Jane's payment was credited on the 21st day of the billing cycle.
(2)  The average daily balance through the 25th day of the billing cycle was $540.

71. (B)  -------题中问的total salary不是没变么,只是人数变了啊.---total of the combined salary什么意思?
  
On July 1 of last year, the total number of employees at Company E was decreased by 10 percent.  Without any change in the salaries of the remaining employees, the average (arithmetic mean) employee salary was 10 percent more after the decrease in number of employees than before the decrease.  The total of the combined salaries of all of the employees at Company E after July 1 last year was what percent of that before July 1 last year?

(A) 90%
(B) 99%
(C) 100%
(D) 101%
(E) 110%

tulipmontrealer

90. (D)
On Jane's credit card account, the average daily balance for a 30-day billing cycle is the average (arithmetic mean) of the daily balances at the end of each of the 30 days.  At the beginning of a certain 30-day billing cycle, Jane's credit card account had a balance of $600.  Jane made a payment of $300 on the account during the billing cycle.  If no other amounts were added to or subtracted from the account during the billing cycle, what was the average daily balance on Jane's account for the billing cycle?
(1)  Jane's payment was credited on the 21st day of the billing cycle.
(2)  The average daily balance through the 25th day of the billing cycle was $540.

這題就是說，一個信用循環是30天，
JANE在一個信用循環裡刷了六百塊，還了三百，請問每日平均欠款（餘額）是多少。
條件一，她在第21天還錢，那平均餘額就是600*20 + 300*10除以30天，可解題。
條件二，她在第25天時平均餘額是540，既然到25天平均不是600，就表示她已經還錢了，
所以剩下的天數都是欠300，平均餘額是540*25 + 300*5除以30天，可解題。

71. (B)  -------题中问的total salary不是没变么,只是人数变了啊.---total of the combined salary什么意思?
  
On July 1 of last year, the total number of employees at Company E was decreased by 10 percent.  Without any change in the salaries of the remaining employees, the average (arithmetic mean) employee salary was 10 percent more after the decrease in number of employees than before the decrease.  The total of the combined salaries of all of the employees at Company E after July 1 last year was what percent of that before July 1 last year?

(A) 90%
(B) 99%
(C) 100%
(D) 101%
(E) 110%

這題就是問裁員後總薪資是裁員前總薪資的多少比例。
設裁員前人數X，平均薪資Y，總薪資XY
裁員後人數0.9X，平均薪資1.1Y，總薪資0.99XY，
0.99/1＊100％＝99％。

anonym1106

第一题：

题干定义了ＡＤＢ，然后说了一个例子．这个人刚开始的ＡＤＢ为６００，有一次付了３００，就是剩下３００．根据定义，其实只要知道是哪天付出去的就可以起初这个月的ＡＤＢ．

（１）可以

（２）告诉你前２５天的ＡＤＢ（说明在２５天前已经付出钱了，如果要算的话，也可以，列个方程，求出是第１５天付出的），然后后５天的ＡＤＢ就是３００（因为没有变化了）．so,可以！

答案D!

exhilarating

非常谢谢二位!!!!

71. (B)  -------  
On July 1 of last year, the total number of employees at Company E was decreased by 10 percent.  Without any change in the salaries of the remaining employees, the average (arithmetic mean) employee salary was 10 percent more after the decrease in number of employees than before the decrease.  The total of the combined salaries of all of the employees at Company E after July 1 last year was what percent of that before July 1 last year?

我怎么觉得题目自相矛盾???虽然算是算出来了.....

题中红色字体不是说了"total salary没变, 只是人均变成了10% more" . 既然总的salary没变,怎么还问那个问题?