PREP2 请教4题!!!

ktj

43.(D)
A college admissions officer predicts that 20 percent of the students who are accepted will not attend the college.  According to this prediction, how many students should be accepted to achieve a planned enrollment of x students?
(A) 1.05x
(B) 1.1x
(C) 1.2x
(D) 1.25x
(E) 1.8x

38.(C)
A certain business produced x rakes each month from November through February and shipped 0.5x rakes at the beginning of each month from March through October.  The business paid no storage costs for the rakes from November through February, but it paid storage costs of $0.10 per rake each month from March through October for the rakes that had not been shipped.  In terms of x, what was the total storage cost, in dollars, that the business paid for the rakes for the 12 months from November through October?
(A) 0.40x
(B) 1.20x
(C) 1.40x
(D) 1.60x
(E) 3.20x

162. (A)
If n is a positive integer and r is the remainder when n^2 - 1 is divided by 8, what is the value of r ?
(1) n is odd
(2) n is not divisible by 8.

176. (C)
In 1995 Division A of Company X had 4,850 customers.  If there were 86 service errors in Division A that year, what was the service-error rate, in number of service errors per 100 customers, for Division B of Company X in 1995 ?
(1) In 1995 the overall service-error rate for Divisions A and B combined was 1.5 service errors per 100 customers.
(2) In 1995 Division B had 9,350 customers, none of whom were customers of Division A.

racing78

以下是引用ktj在2007-10-28 23:47:00的发言：

43.(D)
A college admissions officer predicts that 20 percent of the students who are accepted will not attend the college.  According to this prediction, how many students should be accepted to achieve a planned enrollment of x students?
(A) 1.05x
(B) 1.1x
(C) 1.2x
(D) 1.25x
(E) 1.8x

x/(1-0.2)=1.25x

38.(C)
A certain business produced x rakes each month from November through February and shipped 0.5x rakes at the beginning of each month from March through October.  The business paid no storage costs for the rakes from November through February, but it paid storage costs of $0.10 per rake each month from March through October for the rakes that had not been shipped.  In terms of x, what was the total storage cost, in dollars, that the business paid for the rakes for the 12 months from November through October?
(A) 0.40x
(B) 1.20x
(C) 1.40x
(D) 1.60x
(E) 3.20x

3月:3.5x 4月:3x......9月:0.5x

cost=0.1x(3.5x+...+0.5x)x7/2=1.4x

162. (A)
If n is a positive integer and r is the remainder when n^2 - 1 is divided by 8, what is the value of r ?
(1) n is odd
(2) n is not divisible by 8.

n^2-1=(n+1)(n-1),如果n是奇數又>0,最小為1,n^2-1=0除以8餘數為0,若n>=3時,(n+1)(n-1)必為8之倍數

所以餘數為0,A is sufficient

B的話隨便舉兩個例就知道不充分

176. (C)
In 1995 Division A of Company X had 4,850 customers.  If there were 86 service errors in Division A that year, what was the service-error rate, in number of service errors per 100 customers, for Division B of Company X in 1995 ?
(1) In 1995 the overall service-error rate for Divisions A and B combined was 1.5 service errors per 100 customers.
(2) In 1995 Division B had 9,350 customers, none of whom were customers of Division A.

Ea/Ca=86/4850,依題目可知要求Eb/Cb,根據A條件顯然無法滿足,因為(Ea+Eb)/(Ca+Cb)=1.5/100,一條方程式無法解兩個未知數,同理B條件亦無法單獨求出,結合AB後,可求出Eb,所以Eb/Cb可得.

ktj

多谢RACING78! 仍有几个问题..

以下是引用racing78在2007-10-29 9:03:00的发言：

43.(D)
A college admissions officer predicts that 20 percent of the students who are accepted will not attend the college.  According to this prediction, how many students should be accepted to achieve a planned enrollment of x students?
(A) 1.05x
(B) 1.1x
(C) 1.2x
(D) 1.25x
(E) 1.8x

x/(1-0.2)=1.25x     本题什么意思?没读懂...

38.(C)
A certain business produced x rakes each month from November through February and shipped 0.5x rakes at the beginning of each month from March through October.  The business paid no storage costs for the rakes from November through February, but it paid storage costs of $0.10 per rake each month from March through October for the rakes that had not been shipped.  In terms of x, what was the total storage cost, in dollars, that the business paid for the rakes for the 12 months from November through October?
(A) 0.40x
(B) 1.20x
(C) 1.40x
(D) 1.60x
(E) 3.20x

3月:3.5x 4月:3x......9月:0.5x      本题什么意思?没读懂... 

cost=0.1x(3.5x+...+0.5x)x7/2=1.4x

162. (A)
If n is a positive integer and r is the remainder when n^2 - 1 is divided by 8, what is the value of r ?
(1) n is odd
(2) n is not divisible by 8.

n^2-1=(n+1)(n-1),如果n是奇數又>0,最小為1,n^2-1=0除以8餘數為0,若n>=3時,(n+1)(n-1)必為8之倍數

所以餘數為0,A is sufficient

B的話隨便舉兩個例就知道不充分

176. (C)
In 1995 Division A of Company X had 4,850 customers.  If there were 86 service errors in Division A that year, what was the service-error rate, in number of service errors per 100 customers, for Division B of Company X in 1995 ?
(1) In 1995 the overall service-error rate for Divisions A and B combined was 1.5 service errors per 100 customers.
(2) In 1995 Division B had 9,350 customers, none of whom were customers of Division A.

Ea/Ca=86/4850,依題目可知要求Eb/Cb,根據A條件顯然無法滿足,因為(Ea+Eb)/(Ca+Cb)=1.5/100,一條方程式無法解兩個未知數,同理B條件亦無法單獨求出,結合AB後,可求出Eb,所以Eb/Cb可得.

racing78

第一題：如果預期會有20%的人沒來，那麼要達到100%的入學率，實際上必需要admit125%的人才行

所以假設x為百分之百入學之人數，那麼扣除20%可能不來的，實際要admit125%也就是x/(1-20%)=125%

第二題：工廠11~2月每個月製造x件物品，3~10月平均每月賣出0.5X,所以3月賣出0.5X，到3月的庫存剩下3.5x,依照題意要付0.1 x 3.5x的倉儲成本=0.35x,依此類推工廠只要付7個月就好，因為過了8個月可把東西

全賣光。應用一下等差級數概念很容易就能求出.

ktj

THANKS!

汗...so easy的题目...一时没读懂.....