GMAT Prep Maths Problems

自由心证 · 发表于 2009-11-23 09:59:33

Hello,

接上贴。希望CDer能够帮忙看看正确答案是什么，并且给我一点思路，谢谢。

Hello,

以下是几道GMAT Prep上我做错的题。我的数学错了12个！而且1个礼拜后就开考了。希望CDer能够帮忙看看正确答案是什么，并且给我一点思路，谢谢。

1．If n is a positive integer less than 200 and 14n/60 is an integer, then n has how many different positive prime factors?

A. Two

B. Three

C. Five

D. Six

E. Eight

为什么答案不是D?

2．Before being simplified, the instructors for computing income tax in Country R were to add 2 percent of one’s annual income to the average (arithmetic mean) of 100 units of Country R’s currency and 1 percent of one’s annual income. Which of the following represents the simplified formula for computing the income tax, in country R’s currency, for a person in that country whose annual income is 1?

A. 50+I200

B. 50+3I/100

C. 50+I/40

D. 100+I/50

E. 100+3I/100

请问答案是什么？

3．If x^4+y^4=100, then the greatest possible value of x is between

A. 0 and 3

B. 3 and 6

C. 6 and 9

D. 9 and 12

E. 12 and 15

为什么答案不是A?

4．If z^n =1,what is the value of z?

(1) n is a nonzero integer

(2) z>0

为什么答案不是A?

Stock	Number of shares
V	68
W	112
X	56
Y	94
Z	45

5．The table shows the number of shares of each of the 5 stocks owned byMr. Sami. If Mr. Sami was to sell 20 shares of Stock X and buy 24 shares of stock Y, what would be the increase in the range of the numbers of shares of the 5 stocks owned by Mr. Sami?

A. 4

B. 6

C. 9

D. 15

E. 20

为什么答案不是A?

谢谢！

Anonymos · 发表于 2009-11-23 12:53:23

1.因为n小于200，所以n=2*3*5 选B
2.2%(I) + (100 + 1%(I))/2 间化，选C
3.x^4=100,开根，选B
4.条件1单独不能确定Z的值，Z可为正负1。
5.注意问的是range，没有买卖之前的range是45 ~112，变化之后的range是36～118，increase in the range 应该是（118-36）-（112-45）=15，选D

longlongalex · 发表于 2009-11-23 13:13:00

1．If n is a positive integer less than 200 and 14n/60 is an integer, then n has how many different positive prime factors?

A. Two

B. Three

C. Five

D. Six

E. Eight

14n/60,可以写成2*7*n/2*2*3*5=7*n/2*3*5.若为整数，则n的质因子有2，3，5。选B.
这种题目你举一数做例子就可以了。记住2也是质数，是唯一的偶质数。

2．Before being simplified, the instructors for computing income tax in Country R were to add 2 percent of one’s annual income to the average (arithmetic mean) of 100 units of Country R’s currency and 1 percent of one’s annual income. Which of the following represents the simplified formula for computing the income tax, in country R’s currency, for a person in that country whose annual income is 1?

A. 50+I200

B. 50+3I/100

C. 50+I/40

D. 100+I/50

E. 100+3I/100
这道题的意思是收入的tax=%2的收入＋（1％的收入与100个货币单位的平均数）＝％2*I+(1%*I+100)/2=C

请问答案是什么？

3．If x^4+y^4=100, then the greatest possible value of x is between

A. 0 and 3

B. 3 and 6

C. 6 and 9

D. 9 and 12

E. 12 and 15

为什么答案不是A?
这道题没说x和y是整数。选B

4．If z^n =1,what is the value of z?

(1) n is a nonzero integer

(2) z>0

为什么答案不是A?
（1）只能得出Z＝1或z=-1,(1)＋（2）＝sufficient

Stock	Number of shares
V	68
W	112
X	56
Y	94
Z	45

5．The table shows the number of shares of each of the 5 stocks owned byMr. Sami. If Mr. Sami was to sell 20 shares of Stock X and buy 24 shares of stock Y, what would be the increase in the range of the numbers of shares of the 5 stocks owned by Mr. Sami?

A. 4

B. 6

C. 9

D. 15

E. 20

为什么答案不是A? range就是最大值减最小值，原来的range是112－45。现在的range是新的Y-新的X，即118.04-44.8，和原来的range比，选B.

自由心证 · 发表于 2009-11-23 13:25:33

谢谢，各位的解释很好很强大。

GMAT Prep Maths Problems

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