PREP-PS题有四道方法太费时,请教简单可操作的方法.

maomm

65.       7870-!-item-!-187;#058&005675

For how many integers n is 2^n = n^2 ?

 

(A) None

(B) One

(C) Two

(D) Three

(E) More than three

答案是2，4，可是一紧张只能想到2，怎么才能很快判断出4也符合条件呢？

68.       8012-!-item-!-187;#058&005726

The number 75 can be written as the sum of the squares of 3 different positive integers.  What is the sum of these 3 integers?

 

(A) 17

(B) 16

(C) 15

(D) 14

(E) 13

我用的笨办法是：从最大的8开始往下推，直到推出7，5，1来，有没有更科学的方法呢？

 

88.       10039-!-item-!-187;#058&007071

At a certain college there are twice as many English majors as history majors and three times as many English majors as mathematics majors.  What is the ratio of the number of history majors to the number of mathematics majors?

 

(A) 6 to 1

(B) 3 to 2

(C) 2 to 3

(D) 1 to 5

(E) 1 to 6

twice as many English majors as history majors 我觉得是2*E=H,而下面一题,表达一样,却不是一个含义

这题同DS-1-61题,

61.       5157-!-item-!-187;#058&004472

Of the 60 animals on a certain farm,  [?] are either pigs or cows.  How many of the animals are cows?

 

(1)  The farm has more than twice as many cows as it has pigs.C>2P,

 

(2)  The farm has more than 12 pigs.

遇到这类表达,到底是指谁大呢? 好像在考语法似的.

117.     11706-!-item-!-187;#058&007820

A certain office supply store stocks 2 sizes of self-stick notepads, each in 4 colors:  blue, green, yellow, or pink.  The store packs the notepads in packages that contain either 3 notepads of the same size and the same color or 3 notepads of the same size and of

3 different colors.  If the order in which the colors are packed is not considered, how many different packages of the types described above are possible?

 

(A)  6

(B)  8

(C)  16

(D)  24

(E)  32

这题我的思路是:2(SIZE)*4(COLOR)+2(SIZE)*C(3,4), 不知思路对吗?

非常感谢回复,本人数学确实太差了.

88.       10039-!-item-!-187;#058&007071

At a certain college there are twice as many English majors as history majors and three times as many English majors as mathematics majors.  What is the ratio of the number of history majors to the number of mathematics majors?

 

(A) 6 to 1

(B) 3 to 2

(C) 2 to 3

(D) 1 to 5

(E) 1 to 6

twice as many English majors as history majors 我觉得是2*E=H,而下面一题,表达一样,却不是一个含义

这题同DS-1-61题,

61.       5157-!-item-!-187;#058&004472

Of the 60 animals on a certain farm,  [?] are either pigs or cows.  How many of the animals are cows?

 

(1)  The farm has more than twice as many cows as it has pigs.C>2P,

 

(2)  The farm has more than 12 pigs.

遇到这类表达,到底是指谁大呢? 好像在考语法似的.

117.     11706-!-item-!-187;#058&007820

A certain office supply store stocks 2 sizes of self-stick notepads, each in 4 colors:  blue, green, yellow, or pink.  The store packs the notepads in packages that contain either 3 notepads of the same size and the same color or 3 notepads of the same size and of

3 different colors.  If the order in which the colors are packed is not considered, how many different packages of the types described above are possible?

 

(A)  6

(B)  8

(C)  16

(D)  24

(E)  32

这题我的思路是:2(SIZE)*4(COLOR)+2(SIZE)*C(3,4), 不知思路对吗?

非常感谢回复,本人数学确实太差了.

 

ChrisCong

第一题,往两条曲线的形状上想,就简单了.

第二题，你的思路非常对头，考试的时候，做出答案就是硬道理．

之后是个老生常谈的语法问题，２倍和多两倍的不同，前者是２，后者是３．

2(SIZE)*4(COLOR)+2(SIZE)*C(3,4), 不知思路对吗?　我也这么想，把either or 分别算了，加起来．

maomm

谢谢你的热心回复哈.

但是第三题我还是不明白的是,2倍的那题表达是:2ENGLISH= HISTORY,那按这种思路下来,FARM那题,多2倍,我的推理是P>2C,而正确答案是C>2P,这是怎么回事呢?

再次感谢回复