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[原始] 求教2道个位数整除问题(>﹏<)

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楼主
发表于 2016-5-20 19:29:11 | 只看该作者 回帖奖励 |倒序浏览 |阅读模式
求教两道数学题,刚刚在GMATpill上做到的,两道题长得很像,都没有思路...X﹏X
第一道

892,132,25x
If x represents the units digit of the number above, what is the value of x?
(1) The number above is divisible by 2.
(2) The number above is divisible by 8.
(A)

Statement 1 alone is sufficient but statement 2 alone is not sufficient to answer the question asked.

(B)

Statement 2 alone is sufficient but statement 1 alone is not sufficient to answer the question asked.

(C)

Both statements 1 and 2 together are sufficient to answer the question but neither statement is sufficient alone.

(D)

Each statement alone is sufficient to answer the question.

(E)

Statements 1 and 2 are not sufficient to answer the question asked and additional data is needed to answer the statements.



第二道
261,634,24x
If x represents the units digit of the number above, what is the value of x?
(1) The number above is divisible by 9.
(2) The number above is divisible by 12.
(A)

Statement 1 alone is sufficient but statement 2 alone is not sufficient to answer the question asked.

(B)

Statement 2 alone is sufficient but statement 1 alone is not sufficient to answer the question asked.

(C)

Both statements 1 and 2 together are sufficient to answer the question but neither statement is sufficient alone.

(D)

Each statement alone is sufficient to answer the question.

(E)

Statements 1 and 2 are not sufficient to answer the question asked and additional data is needed to answer the statements.



另外下面是在GMATclub上找到的很像的题的解答,
892,132,24x

If x represents the units digit of the number above, what is the value of x?


(1) The number above is divisible by 2 --> x is even. Not sufficient.

(2) The number above is divisible by 6 --> 8+9+2+1+3+2+2+4+x=31+x --> x could be 2 or 8 (in this case the number will be even, so divisible by 2 and the sum of its digits will be a multiple of 3, thus it will be divisible by 3). Not sufficient.

(1)+(2) x could be 2 or 8. Not sufficient.

Answer: E.


LZ比较笨(>﹏<),看了这个解答也还是不知道上面两道题肿么做,OA的话只知道第一道不是E,第二道不是B,求教求教.....
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沙发
发表于 2016-5-20 21:30:10 | 只看该作者
对于第一题,条件1若充分,x可以是0,2,4,6,8;条件2若充分,x可以是6(末三位是8的倍数);所以,BorC.
对于第二题,条件1若充分,x=6(数字和是9的倍数);条件2若充分,x=0(数字和是3的倍数,末两位是4的倍数).所以,C.
板凳
发表于 2016-5-21 12:21:59 | 只看该作者
当整数各位的和能被3除余几,这个整数被3除余几
当最后三位被8除余几,这个整数被8除余几
最后两位被4除
各位的和被3除
地板
发表于 2016-5-21 12:29:59 | 只看该作者
第一题是B,被8除要余数是0,x必然是6,选B
第二题,被9除,x为8,被12除就是能被3和4除,被3除,x=2,5,8,被4除,x=0,4,8,所以X=8,选D
5#
 楼主| 发表于 2016-5-21 13:36:16 | 只看该作者
Robinchen1001 发表于 2016-5-21 12:29
第一题是B,被8除要余数是0,x必然是6,选B
第二题,被9除,x为8,被12除就是能被3和4除,被3除,x=2,5,8, ...

(⊙▽⊙) 啊,懂啦!谢谢呀~
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