GWD数学错误率从前天的28降到16了,再来请教问题

maomm · 发表于 2007-5-24 02:27:00

Q2:

When positive integer x is divided by positive integer y, the remainder is 9. If x/y = 96.12, what is the value of y?

A. 96

B. 75

C. 48

D. 25

E. 12

现在一遇到余数问题，就无从下手，有统一公式可参考吗？

Q3:

Is the standard deviation of the salaries of Company Y’s employees greater than the standard deviation of the salaries of Company Z’s employees?

(1) The average (arithmetic mean) salary of Company Y’s employees is greater than the average salary of Company Z’s employees.

(2) The median salary of Company Y’s employees is greater than the median salary of Company Z’s employees.

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.

（1）的错误是因为“数据分布离平均值越近，方差越小”，但此处Y，Z公司的各自数值未知吗？

6.

The figure above shows the dimensions of a semicircular cross section of a one-way tunnel. The single traffic lane is 12 feet wide and is equidistant from the sides of the tunnel. If vehicles must clear the top of the tunnel by at least ½ foot when they are inside the traffic lane, what should be the limit on the height of vehicles that are allowed to use the tunnel?

A. 5½ ft

B. 7½ ft

C. 8 ½ ft

D. 9½ ft

E. 10 ft

我不明白这里的12FT，与20FT有什么关系？答案B是由20-12-1/2来的吗？可我不懂原理，我已经查了NN的讨论贴了。

Q7:

Square S is inscribed in circle T. If the perimeter of S is 24, what is the circumference of T?

A. 6p

B. 12p

C. 3Ö2 p

D. 6Ö2 p

E. 12Ö2 p

我是估算出6Ö2 p，但不知正确运算过程

Q8:

The operation Ä is defined for all nonzero numbers a and b by a Ä b = a/b – b/a. If x and y are nonzero numbers, which of the following statements must be true?

I. x Ä xy = x(1 Ä y)

II. x Ä y = -(y Ä x)

III. 1/x Ä 1/y = y Ä x

A. I only

B. II only

C. III only

D. I and II

E. II and III

这种题目的做题思路就是把Ä
这类怪字符化解掉先吗？我做了觉得A也是对的呀？请高N指教！

Q9:

What was the price at which a merchant sold a certain appliance?

(1) The merchant’s gross profit on the appliance was 20 percent of the price at which the merchant sold the appliance.

(2) The price at which the merchant sold the appliance was $50 more than the merchant’s cost of the appliance.

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.

(1)利润= 20%价格,可是条件中的利润也是未知数,如何导出价格呢?

(2)价格=50+成本, 成本也未知呀?

Q12:

There are 11 women and 9 men in a certain club. If the club is to select a committee of 2 women and 2 men, how many different such committees are possible?

A. 120

B. 720

C. 1,060

D. 1,520

E. 1,980

请问公式是不是C（2，11）/C（2，20）+C（2，9）/C（2，18）？

Q26:a shelf, of which 2 are paperbacks and 6 are hardbacks. How many possible selections of 4 books from this self include at least one paperback?

A. 40

B. 45

C. 50

D. 55

E. 60

我不知道是该用P还是用C, 我用的是C(1,4)+C(2,8)

Q31:

There are 8 magazines lying on a table; 4 are fashion magazines and the other 4 are sports magazines. If 3 magazines are to be selected at random from the 8 magazines, what is the probability that at least one of the fashion magazines will be selected?

A. 1/2

B. 2/3

C. 32/35

D. 11/12

E. 13/14

Q31:

There are 8 magazines lying on a table; 4 are fashion magazines and the other 4 are sports magazines. If 3 magazines are to be selected at random from the 8 magazines, what is the probability that at least one of the fashion magazines will be selected?

A. 1/2

B. 2/3

C. 32/35

D. 11/12

E. 13/14

排列,组合我虽然看了书上的例题都懂,可一遇到真题,就不知道用C还是用P了,还有用C也用P,它们之间是+还是*, 真乱...

Q24:

The value of (9´10⁷)(9´10⁸) is closest to which of the following?

A. 10¹⁶

B. 10¹⁷

C. 10⁵⁶

D. 10⁵⁷

E. 10⁵⁸

是不是因为(9´107)(9´108)=(10^1-1) ´107´(10^1-1) ´108

Q32:

What is the remainder when the two digit, positive integer x is divided by 3?

(1)
The sum of the digits of x is 5.

(2)
The remainder when x is divided by 9 is 5.

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.

我是指带值计算的，带9的倍数再加上题中给的余数得出的，但有没有推导公式呢，我这种有时会漏掉什么值的

真的感觉到我问的数学问题都比起大家来,简单得不行,但就是基础太差了,现在在一边陈向东一边GWD,可一遇到新题就啥都忘记了,看来真要多多练习了.真心谢谢大家对我的帮助,我曾经一度都想放弃GMAT了,因为大家数学都是50,51,我要即攻数学也打语文,好累呀....

maomm · 发表于 2007-5-24 19:09:00

主要身边没有人可以问, 真的自己想不通,才来请教大家的.数学太烂了,谢谢

xiaoyue00302 · 发表于 2007-5-24 22:04:00

Q2:75
解:9/0.12=75

Q3:E
如楼主所说,标准方差与均值和中值无关

Q6:这是PREP的题
   勾股定理: h^2=(20/2)*(20/2)-(12/2)*(12/2)=64
             h=8
车顶与隧道顶至少距离0.5,故
             H=8-0.5=7.5

Q7: 正方形边长24/4=6
     圆半径,依勾股定理: 6^2=2r^2
                        r=3倍根2
     圆周长: 2pai* 3倍根2=6pai倍根2

Q8:这题恐怕你得自己做,我尝试了一下,实在说不清楚,不能化简那个符号.

Q9: C
   价格的20%是利润
   50也是利润
   50/20%= the price sold a certain appliance

先这样吧

建议你还是先上个辅导班比较好，我觉得这样下去对你的提高不利

[此贴子已经被作者于2007-5-24 22:20:22编辑过]

如果传说 · 发表于 2007-5-24 23:10:00

以下是引用maomm在2007-5-24 2:27:00的发言：

Q2:

When positive integer x is divided by positive integer y, the remainder is 9. If x/y = 96.12, what is the value of y?

A. 96

B. 75

C. 48

D. 25

E. 12

现在一遇到余数问题，就无从下手，有统一公式可参考吗？

一个数(X)被另一个数(Y)除,余C,都可以写成X=AY+C(A是商,不知具体值一般不会影响解题).具体到这题:X=AY+9,X/Y=(AY+9)/Y=96.12,

即:Y=9/(96.12-A),当A取96时,可以得到整数Y=75

Q3:

Is the standard deviation of the salaries of Company Y’s employees greater than the standard deviation of the salaries of Company Z’s employees?

(1) The average (arithmetic mean) salary of Company Y’s employees is greater than the average salary of Company Z’s employees.

(2) The median salary of Company Y’s employees is greater than the median salary of Company Z’s employees.

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.

（1）的错误是因为“数据分布离平均值越近，方差越小”，但此处Y，Z公司的各自数值未知吗？

看到统计我就犯晕,感觉应该选E吧,两个结合在一起也不充分,可以举个例子:设

Y公司有2人,每人工资都是10;则arithmetic mean=10,median=10;方差=0

Z公司有2人,每人工资都是5;则arithmetic mean=5,median=5;方差=0

此时满足条件(1)和(2),Y=Z,但当其中任一个数字变化(比如工资变成不一样),必定是不等式的关系

6.

The figure above shows the dimensions of a semicircular cross section of a one-way tunnel. The single traffic lane is 12 feet wide and is equidistant from the sides of the tunnel. If vehicles must clear the top of the tunnel by at least ½ foot when they are inside the traffic lane, what should be the limit on the height of vehicles that are allowed to use the tunnel?

A. 5½ ft

B. 7½ ft

C. 8 ½ ft

D. 9½ ft

E. 10 ft

我不明白这里的12FT，与20FT有什么关系？答案B是由20-12-1/2来的吗？可我不懂原理，我已经查了NN的讨论贴了。

个人理解:那条车行道恰好从隧道的正中间过去，也就是说,以圆心为中心左右各延伸出3FT是车可以走的地方;由此可以求出,汽车碰到隧道时高度必为8FT(勾股定理,根号下10²-6²),题目要求当在隧道中的汽车的顶部与隧道壁之间最少要有1/2FT的距离，那么能够使用这个隧道的汽车的限高就是8-1/2选B

Q7:

Square S is inscribed in circle T. If the perimeter of S is 24, what is the circumference of T?

A. 6p

B. 12p

C. 3Ö2 p

D. 6Ö2 p

E. 12Ö2 p

我是估算出6Ö2 p，但不知正确运算过程

正方形周长24,可得正方形边长4.圆形有一个定理:圆周角如果是90度,其对应的斜边必是直径,所以可求得圆的直径=根号下6²+6²=6Ö2,圆周长=直径*p= 6Ö2 p

Q8:

The operation Ä is defined for all nonzero numbers a and b by a Ä b = a/b – b/a. If x and y are nonzero numbers, which of the following statements must be true?

I. x Ä xy = x(1 Ä y)

II. x Ä y = -(y Ä x)

III. 1/x Ä 1/y = y Ä x

A. I only

B. II only

C. III only

D. I and II

E. II and III

这种题目的做题思路就是把Ä
这类怪字符化解掉先吗？我做了觉得A也是对的呀？请高N指教！

x Ä xy = X/XY-XY/X=1/Y-Y

x(1 Ä y) 要分两步做,先做:1 Ä y=1/Y-Y,再乘以X,与前式显然不等

Q9:

What was the price at which a merchant sold a certain appliance?

(1) The merchant’s gross profit on the appliance was 20 percent of the price at which the merchant sold the appliance.

(2) The price at which the merchant sold the appliance was $50 more than the merchant’s cost of the appliance.

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.

(1)利润= 20%价格,可是条件中的利润也是未知数,如何导出价格呢?

(2)价格=50+成本, 成本也未知呀?

题目的隐含条件是:利润=售价-成本

Q12:

There are 11 women and 9 men in a certain club. If the club is to select a committee of 2 women and 2 men, how many different such committees are possible?

A. 120

B. 720

C. 1,060

D. 1,520

E. 1,980

请问公式是不是C（2，11）/C（2，20）+C（2，9）/C（2，18）？

为什么还要除呢?直接从11个女的里选两人C（2，11）,再加上从9个男的里选2人C（2，9）这行了

Q26:a shelf, of which 2 are paperbacks and 6 are hardbacks. How many possible selections of 4 books from this self include at least one paperback?

A. 40

B. 45

C. 50

D. 55

E. 60

我不知道是该用P还是用C, 我用的是C(1,4)+C(2,8)

没有顺序的问题,两本书是同时拿的,所以用C,不用P,求这两本里至少有一本是PAPERBACK

第一种可能:C(1,2)*C(1,6),P里取一本,H里取一本

第二种可能:C(2,2),直接从P里取两本

以上两种加一起好了

Q31:

There are 8 magazines lying on a table; 4 are fashion magazines and the other 4 are sports magazines. If 3 magazines are to be selected at random from the 8 magazines, what is the probability that at least one of the fashion magazines will be selected?

A. 1/2

B. 2/3

C. 32/35

D. 11/12

E. 13/14

Q31:

There are 8 magazines lying on a table; 4 are fashion magazines and the other 4 are sports magazines. If 3 magazines are to be selected at random from the 8 magazines, what is the probability that at least one of the fashion magazines will be selected?

A. 1/2

B. 2/3

C. 32/35

D. 11/12

E. 13/14

排列,组合我虽然看了书上的例题都懂,可一遇到真题,就不知道用C还是用P了,还有用C也用P,它们之间是+还是*, 真乱...

Q24:

The value of (9´10⁷)(9´10⁸) is closest to which of the following?

A. 10¹⁶

B. 10¹⁷

C. 10⁵⁶

D. 10⁵⁷

E. 10⁵⁸

是不是因为(9´107)(9´108)=(10^1-1) ´107´(10^1-1) ´108

Q32:

What is the remainder when the two digit, positive integer x is divided by 3?

(1)
The sum of the digits of x is 5.

(2)
The remainder when x is divided by 9 is 5.

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.

我是指带值计算的，带9的倍数再加上题中给的余数得出的，但有没有推导公式呢，我这种有时会漏掉什么值的

真的感觉到我问的数学问题都比起大家来,简单得不行,但就是基础太差了,现在在一边陈向东一边GWD,可一遇到新题就啥都忘记了,看来真要多多练习了.真心谢谢大家对我的帮助,我曾经一度都想放弃GMAT了,因为大家数学都是50,51,我要即攻数学也打语文,好累呀....

回答了一半发现已经有人回复了,就不继续写下去了,

maomm · 发表于 2007-5-25 09:25:00

谢谢两位的回复,很感谢.

我在北美,估计没有培训班可上了.见笑了,数学太烂了.

无所事事 · 发表于 2007-5-25 13:34:00

谢谢，里面有几题我也一直困惑。看到答案觉得很简单，但自己做时又不知从何下手。

有个小问题

个人理解:那条车行道恰好从隧道的正中间过去，也就是说,以圆心为中心左右各延伸出3FT是车可以走的地方;由此可以求出,汽车碰到隧道时高度必为8FT(勾股定理,根号下10²-6²),

应该是6FT吧，呵呵，班门弄斧一下。

如果传说 · 发表于 2007-5-25 14:17:00

以下是引用无所事事在2007-5-25 13:34:00的发言：

谢谢，里面有几题我也一直困惑。看到答案觉得很简单，但自己做时又不知从何下手。

有个小问题

个人理解:那条车行道恰好从隧道的正中间过去，也就是说,以圆心为中心左右各延伸出3FT是车可以走的地方;由此可以求出,汽车碰到隧道时高度必为8FT(勾股定理,根号下10²-6²),

应该是6FT吧，呵呵，班门弄斧一下。

呵呵,谢谢指出,打错了

michelle1021 · 发表于 2007-5-25 18:44:00

好好复习数学一定会很快提高的!

maomm · 发表于 2007-5-26 02:13:00

谢谢MICHELLE,我的数学从没有复习的PREP38提到了复习了两周后的44,有进步了,我好高兴.但是还是错了14题,

GWD数学错误率从前天的28降到16了,再来请教问题

GWD数学错误率从前天的28降到16了,再来请教问题

请大家教我点思路吧,非常非常的感谢

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