several prep questions

hellokelly · 发表于 2009-3-24 02:30:00

x and y are positive integers, what is the value of xy ?

(1) The greatest common factor of x and y is 10.

(2) The least common multiple of x and y is 180.

C

If n and t are positive integers, what is the greatest prime factor of the product nt ?

(1) The greatest common factor of n and t is 5.

(2) The least common multiple of n and t is 105.
B
those two questions are so similar, but why one is c and one is b?

Each employee on a certain task force is either a manager or a director. What percent of the employees on the task force are directors?

(1) The average (arithmetic mean) salary of the managers on the task force is $5,000 less than the average salary of all employees on the task force.

(2) The average (arithmetic mean) salary of the directors on the task force is $15,000 greater than the average salary of all employees on the task force.
Chow to deal with this one? why answer is C?

Is |x - y | > |x | - |y | ?

(1) y < x

(2) xy < 0

B
is this formula |x - y | > |x | - |y | always right?
Each employee of Company Z is an employee of either Division X or Division Y, but not both. If each division has some part-time employees, is the ratio of the number of full-time employees to the number of part-time employees greater for Division X than for Company Z ?

(1) The ratio of the number of full-time employees to the number of part-time employees is less for Division Y than for Company Z.

(2) More than half of the full-time employees of Company Z are employees of Division X, and more than half of the part-time employees of Company Z are employees of Division Y.

D
any shortcut? I just calculate whether px/fx+fy>1/2

On a certain sight-seeing tour, the ratio of the number of women to the number of children was 5 to 2. What was the number of men on the sight-seeing tour?

(1) On the sight-seeing tour, the ratio of the number of children to the number of men was 5 to 11.

(2) The number of women on the sight-seeing tour was less than 30.
C

If k is a positive integer, then 20k is divisible by how many different positive integers?

(1) k is prime.

(2) k = 7
B why 1) couldn't ? is it bc k maybe=5?
f Bob produces 36 or fewer items in a week, he is paid x dollars per item. If Bob produces more than 36 items in a week, he is paid x dollars per item for the first 36 items and 1.5 times that amount for each additional item. How many items did Bob produce last week?

(1) Last week Bob was paid a total of $480 for the items that he produced that week.

(2) This week Bob produced 2 items more than last week and was paid a total of $510 for the items that he produced this week.

E

why answer is E? since we could know any extract 2 could be 510-480=30

then extract 1=15, x=10

480=10*36+(n-36)*15

should be C

[此贴子已经被作者于2009-3-24 22:03:04编辑过]

hellokelly · 发表于 2009-3-24 08:06:00

ilhht · 发表于 2009-3-24 12:01:00

If x and y are positive integers, what is the value of xy ?

(1) The greatest common factor of x and y is 10.

(2) The least common multiple of x and y is 180.

C

If n and t are positive integers, what is the greatest prime factor of the product nt ?

(1) The greatest common factor of n and t is 5.

(2) The least common multiple of n and t is 105.

B

第一个题目，有一个公式：两个数的乘积=最小公倍数*最大公约数，所以选C

第二个题目，由于最小公倍数就是包括了两个数字中所有因子的最高次幂的乘积，所以必然包括了质因子乘积，所以B充分

ilhht · 发表于 2009-3-24 12:11:00

Each employee on a certain task force is either a manager or a director. What percent of the employees on the task force are directors?

(1) The average (arithmetic mean) salary of the managers on the task force is $5,000 less than the average salary of all employees on the task force.

(2) The average (arithmetic mean) salary of the directors on the task force is $15,000 greater than the average salary of all employees on the task force.

Chow to deal with this one? why answer is C?

这个题目跟上次那个一样，就是举的例子，现在有两个未知数，需要知道至少两个方程，然不能求出比例。题目说每一个人要么是E要么是D，要求D占总人数的比例，即不知道总人数，也不知道D或者E，根据条件（1)可以假设（M （总工资）+D（宗工资））/（M+D）-M（宗工资）/M=5000，同样由（2）可以得出（D（宗工资））/D+15000=（M（宗工资）+D（宗工资））/（M+D）

这两个式子虽然长的很恶心，但是只有；两个未知数，所以一定可以推出D与M的比例，然后再算D/D+M即可。

作这种题目，只要证明出可以充分得出唯一解即可，不用真的求出是多少。

ilhht · 发表于 2009-3-24 12:15:00

If x and y are positive integers, what is the value of xy ?

(1) The greatest common factor of x and y is 10.

(2) The least common multiple of x and y is 180.

C

If n and t are positive integers, what is the greatest prime factor of the product nt ?

(1) The greatest common factor of n and t is 5.

(2) The least common multiple of n and t is 105.

B
those two questions are so similar, but why one is c and one is b?

Each employee on a certain task force is either a manager or a director. What percent of the employees on the task force are directors?

(1) The average (arithmetic mean) salary of the managers on the task force is $5,000 less than the average salary of all employees on the task force.

(2) The average (arithmetic mean) salary of the directors on the task force is $15,000 greater than the average salary of all employees on the task force.

Chow to deal with this one? why answer is C?

Is |x - y | > |x | - |y | ?

(1) y < x

(2) xy < 0

B

is this formula |x - y | > |x | - |y | always right?

这个题目，要理解他的意思，绝对值x-y表示在数轴上x与y之间的距离，随便举几个数就可以看出，B充分成立。因为xy<0，说明两个数字一个正一个负，所以必然在0的左边和右边，而绝对值x的意思表示x到0的距离，绝对值y的意思表示y到x的距离，很显然B充分推出题目成立。

hang13 · 发表于 2009-3-24 12:26:00

太红了，我眼睛要爆掉了

hellokelly · 发表于 2009-3-24 12:37:00

Thanks a lot mm! Love the cute cat!!! =)))

[此贴子已经被作者于2009-3-24 22:03:31编辑过]

several prep questions

several prep questions

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