求问一道D.S题目！

shuangyun · 发表于 2013-11-13 20:36:47

Whenever Martin has a restaurant bill with an amount between $10 and $99, he calculates the dollar amount of the tip as 2 times the tens digit of the amount of his bill. If the amount of Martin's most recent restaurant bill was between $10 and $99, was the tip calculated by Martin on this bill greater than 15 percent of the amount of the bill?

(1)The amount of the bill was between $15 and $50.

(2)The tip calculated by Martin was $8.

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 statement TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D EACH statement ALONE is sufficient.
E Statements (1) and (2) TOGETHER are NOT sufficient.

答案是B
今天做题脑抽了这道题看了很多遍怎么就是看不懂，求NN翻译&解题思路！万分感谢！！！

还有一道题：

If R=P/Q , is R ≤ P ?

(1) P ＞ 50

(2) 0 ＜ Q ≤ 20

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 statement TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D EACH statement ALONE is sufficient.
E Statements (1) and (2) TOGETHER are NOT sufficient.

答案是E
请问这道题不能直接带入原题的条件，看做是要求0<=P-P/Q 即求是否0<=P(1-1/Q)
此时两个条件共同使用的话，P>0 且1-1/Q始终是大于0的分数数，则原题要求成立，所以选C？？？？

shuangyun · 发表于 2013-11-14 15:25:38

自己顶一下！另外还有一道题非常有疑惑！求NN翻译并给一下解题思路！
Is the integer n odd?

(1)n is divisible by3.

(2)2n is divisible by twice as many positive integers as n.

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 statement TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D  EACH statement ALONE is sufficient.
E  Statements (1) and (2) TOGETHER are NOT sufficient

shuangyun · 发表于 2013-11-15 08:41:10

再顶！请NN解答！！！

shuangyun · 发表于 2013-11-18 09:37:09

UP UP UP UP UP

ann4u · 发表于 2013-11-18 09:58:22

第一道题就是说，小费是总消费（10~99）的十位数的2倍，B选项说小费是8，那么总消费应该是40~49。问题问的是，小费大于总消费的15%吗？总消费10~99,15%的总消费是1.5~14.85，40~49肯定大于15%的总消费啦。选B

ann4u · 发表于 2013-11-18 09:59:37

第二个题，题目并没有告诉P、Q是不是整数，所以是不能确定的，E是对的啦

小盒子eugg · 发表于 2013-11-18 10:08:47

shuangyun 发表于 2013-11-14 15:25
自己顶一下！另外还有一道题非常有疑惑！求NN翻译并给一下解题思路！
Is the integer n odd?

这题是选E吗？有答案吗？
1. 肯定不对啊 n＝6， 6 is even, and is divisible by 3。所以AD错
2. 如果n odd，2n一定even，但even number不一定可以被as many positive odd number约分。所以我觉得2 也错。剩C E
1+2.反证法。如果n＝9，2n的约分 1，3，3，并不是 twice as many positive integer as n

菜鸟分析，求牛人解析！

ann4u · 发表于 2013-11-18 10:12:24

小盒子eugg 发表于 2013-11-18 10:08
这题是选E吗？有答案吗？
1. 肯定不对啊 n＝6， 6 is even, and is divisible by 3。所以AD错
2. 如果n ...

个人觉得这题选C，反正我是特殊值法试出来的~
具体要说的话，就是如果N是偶数，那么N的因子就有2，再乘以2之后，2N的因子怎么也不可能是N的2倍了。

shuangyun · 发表于 2013-11-18 20:00:49

ann4u 发表于 2013-11-18 10:12
个人觉得这题选C，反正我是特殊值法试出来的~
具体要说的话，就是如果N是偶数，那么N的因子就有2，再乘以 ...

这道题是选B
有一个解法原理：
n乘以一个质数a。如果a之前不是n的因子的话，相乘以后，n的所有因子乘以a都会形成一个新的因子，所以n·a的因子个数是n的因子个数的2倍。example：以n=15为例，n有4个因子，1，3，5，15，如果2n=30，有8个，1，2，3，6，5，10，15，30。如果n=6的话，n有4个：1，2，3，6。2n有1，2，3，4，6，12。所以若质数a为2，2n的因子个数为n的两倍，n不能为偶数。
所以从statement2我们可以判断出2不是n的因子，n是odd。

刚开始看这个解题思路完全没有头绪，看不懂，看了你们的想法再重新去看了这个思路才明白！谢谢！

求问一道D.S题目！

所属分类: GMAT考试

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