9月MATHJJ的不解之处,请NN回复

sandyzhuang

A. 106. n>2的整数（138的条件，不影响结果）n=?

1)  11^n的十位数是4

2)  5^n的百位数是6

    我的答案：  E

 

316变体

DS题，问n的个位数是多少？

条件1： 11^n的十位数是4

2：  5^n的百位数是6

选A。

 

碰到这种题目怎么做啊?给点思路

 

B. 有白色花21个和红色花91个，说要拿这些花扎成花束bouquet,每束花里面白色和红色的花个数相等，最多能扎多少束相同的花束？ 

 

答案到底是什么?

 

C. 一个organization里女的占30%，已婚男的占3 / 8，问以下哪个必然对？
                

       Ⅰ女的人数 > 已婚男的人数？
                

         Ⅱ女的人数 > 未婚男的人数
                

         Ⅲ已婚男的人数 > 未婚男的人数
                

 

答案到底是什么?

 

D. 一个数字四舍五入到整数后，与原来的数字不一定相等。用E（I）表示差异和原数的百分比。比如：I=1.5，E（1.5）=33 1/3% 求E（1.6）-E（2.5）
            答案：A 5%  B 33 1/3% 等

 

这题什么思路?

 

E. X^2+Y^2能被5整除吗？
            C

       1. X-Y除5的余数是1

       2.X+Y除5的余数是3   （有变体余数是2）

这题什么思路?

 

F.       说有个三角形，边A、B、C。
            问是否是right angle。
                E
1）A^2+B^2=3^2+4^2
2)  A^2+C^2=3^2+5^2

 

这题答案为什么不是C?

 

G  DS:N IS A FACTOR OF 18200 问N的最大PRIME?

         1）N...

         2）N is a 乘积of 480     答案是B

这题什么思路?

 

 

 

 

whatapain

 一个organization里女的占30%，已婚男的占3 / 8，问以下哪个必然对？
            

       Ⅰ女的人数 > 已婚男的人数？
                

         Ⅱ女的人数 > 未婚男的人数
                

         Ⅲ已婚男的人数 > 未婚男的人数
                

---

simple and workable way is put a number in this kind of problem.

for example: suppose totally number is 100

then 女的人数 = 30; 已婚男的人数=27 (26.5)

      未婚男的人数=70-27=43
                            

---

simple and workable way is put a number in this kind of problem.

for example: suppose totally number is 100

then 女的人数 = 30; 已婚男的人数=27 (26.5)

      未婚男的人数=70-27=43
                

whatapain

A. 106. n>2的整数（138的条件，不影响结果）n=?

1)  11^n的十位数是4

2)  5^n的百位数是6

    我的答案：  E
            

----

this one is sort of unique, when i did that, i use a stupid way, which is to calculate a few n to see what rule it has.

Namely, i multiple 5 get 5(n=1), 25 (n=2) ...till n=8, then I noticed that when n =4, 6, 8,...  百位数是6.

then i did   11^n, i calculated utill n=7, only when n=4,  it has 十位数是4.(actually when n=4, 14, 24, 34.....)

Don't worry, u can just memorize the results, and this one is not easy one, don't worry la.

----

this one is sort of unique, when i did that, i use a stupid way, which is to calculate a few n to see what rule it has.

Namely, i multiple 5 get 5(n=1), 25 (n=2) ...till n=8, then I noticed that when n =4, 6, 8,...  百位数是6.

then i did   11^n, i calculated utill n=7, only when n=4,  it has 十位数是4.(actually when n=4, 14, 24, 34.....)

Don't worry, u can just memorize the results, and this one is not easy one, don't worry la.

-------------------

316变体
            

DS题，问n的个位数是多少？

条件1： 11^n的十位数是4

2：  5^n的百位数是6

选A。
            

-------------------

-------------------

whatapain

D. 一个数字四舍五入到整数后，与原来的数字不一定相等。用E（I）表示差异和原数的百分比。比如：I=1.5，E（1.5）=33 1/3% 求E（1.6）-E（2.5）
            答案：A 5%  B 33 1/3% 等
            

               差异         原数          百分比

E（1.6）      2-1.6=0.4      1.6            25% (0.4/1.6)

    -

E（2.5）      3-2.5=0.5      2.5            20% (0.5/2.5)

    =                                       25%-20%=5%

               差异         原数          百分比

E（1.6）      2-1.6=0.4      1.6            25% (0.4/1.6)

    -

E（2.5）      3-2.5=0.5      2.5            20% (0.5/2.5)

    =                                       25%-20%=5%

whatapain

 X^2+Y^2能被5整除吗？
        C
        

       1. X-Y除5的余数是1

       2.X+Y除5的余数是3   （有变体余数是2）
            

-------

x-y=5a+1; x+y=5b+3       -----------x=5(a+b)/2   + 2;  y= 5(a+b)/2   +1

put x & y into X^2+y^2,    ----------X^2 +y^2 =  25 * (a*a +b*b)/2  + 15b + 5a + 5

since each has a number of 5n, the total number can be divided by 5

-------

x-y=5a+1; x+y=5b+3       -----------x=5(a+b)/2   + 2;  y= 5(a+b)/2   +1

put x & y into X^2+y^2,    ----------X^2 +y^2 =  25 * (a*a +b*b)/2  + 15b + 5a + 5

since each has a number of 5n, the total number can be divided by 5

whatapain

说有个三角形，边A、B、C。
            问是否是right angle。
                E
1）A^2+B^2=3^2+4^2
2)  A^2+C^2=3^2+5^2

this problem is testing ur carefulness, as we know, 3,4,5 can constitute a right triangle.

but what the question says is a^2 +b^2=3^2 +4^2 (which is 25), lots of numbers of a and b can meet this standard (a^2+b^2=25), the question does not tell you that one equals to 3, and the other is 4.

be careful

whatapain

 DS:N IS A FACTOR OF 18200 问N的最大PRIME?

         1）N...

         2）N is a 乘积of 480     答案是B

这题什么思路?

 this JJ is not clear, forget about it unless u have a more complete question description.

Remember JJ is just to show you what kind of problem u might meet, so don't memorize the answer u see online, that's not a right way. key point is to understand the underlying logic.

good luck

 

 this JJ is not clear, forget about it unless u have a more complete question description.

Remember JJ is just to show you what kind of problem u might meet, so don't memorize the answer u see online, that's not a right way. key point is to understand the underlying logic.

good luck

 

sandyzhuang

Thank you so much for your explaination! I will take the GMAT on September 26 in Shanghai. So nervous as AWA and Math are my weakness.

sandyzhuang

more question about the GMAT test: what should I bring to the test center on that day? just my passport? how to choose the school? Shall I take down the school code now and bring it to the test center as what we do for the paper-based toefl test?

What's the best time to arrive there? my schedule time is 9:00 a.m.. Any other suggestions? Thanks a lot

inlovesummer

以下是引用whatapain在2006-9-24 0:37:00的发言：

说有个三角形，边A、B、C。
   问是否是right angle。
    E
1）A^2+B^2=3^2+4^2
2)  A^2+C^2=3^2+5^2

this problem is testing ur carefulness, as we know, 3,4,5 can constitute a right triangle.

but what the question says is a^2 +b^2=3^2 +4^2 (which is 25), lots of numbers of a and b can meet this standard (a^2+b^2=25), the question does not tell you that one equals to 3, and the other is 4.

be careful

请问如果写明是A.BC三边是整数应当可以选A吧